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98 Chapter 5
5.1. INTRODUCTION
The characterization of the crystals is an important tool of the
study of crystals. This helps the crystal grower to assess the quality,
nature and property of the crystals. A large number of experimental
techniques exist to assess the structure, bonding, composition, quality
and the presence of its constituent elements. The experimental methods
include spectroscopic analysis, thermo gravimetric analysis, DSC,
elemental analysis etc. A brief description of the principles involved in
the measurement and salient features of the instruments and
characterization of rare earth mixed oxalate crystals in each case is
given in this chapter.
5.2. X-ray Analysis
X-Ray Powder Diffractometry is the most powerful technique for
structural analysis, capable of providing information about structure of a
material at the atomic level. In this particular case the powder diffraction
method had been employed for the study. Figures 5.1, 5.2, 5.3, 5.4, 5.5, 5.6,
5.7 and 5.8 show the X-ray powder diffractogram of Y2(C2O4)3.14H2O,
Y2Ba(C2O4)4.8H2O,Y2BaCu(C2O4)5.8H2O, Pr2BaCu(C2O4)5.9H2O,
Nd2BaCu(C2O4)5.12H2O, Gd2BaCu(C2O4)5. 13H2O and Dy2BaCu(C2O4)5.12H2O
crystals respectively. The number of water of crystallization of the
Spectroscopic and Thermal Characterization 99
crystals is varied from eight to fourteen in conformation with the results
of thermal analysis.
Hansson1 made a detailed study of the crystals and molecular
structure of Neodymium Oxalate 10.5 Hydrate. Results were similar to
those of decahydrates2. Here also it is seen that whether the water of
crystallisation is varied, it will not affect the crystal structure. The
varying water content observed for these crystals might be explained by
an inclusion of different amounts of water in the cavities depending on
the conditions of crystal growth or slight changes in the growth
environment.
The Bruker D8 Advance X-ray Diffractometer was used to take
the diffraction patterns of the crystals with CuKα radiation of
wavelength λ= 1.5418Å. The samples were scanned over the required
range for 2θ (00 - 800) at a scan speed of 300/s. The analysis of the
spectra confirmed the crystalline nature of the samples. X-ray diffraction
parameters of YOx, YBaOx, YBaCuOx, PrBaCuOx, NdBaCuOx,
GdBaCuOx & DyBaCuOx are given in the table 5.1, the unit cell data of
the crystals are given in the tables 5.2 -5.8 and X-ray diffraction patterns
of the crystals are given in the figures 5.1 –5.7 respectively. It may be
100 Chapter 5
noted that ’d’ values depend on the atomic dimension of the constituent
atoms. It is found that these crystals are of tetragonal system.
Table 5.1 The cell parameters of YOx, YBaOx, YBaCuOx, PrBaCuOx, Nd BaCuOx, GdBaCuOx, & DyBaCuOx.
Crystals a =b(Å) c(Å) α=β=γ (degrees) Volume(Å)3
YOx 10.67 11 90 1252.3379
YBaOx 10.1 12.9 90 1315.929
YBaCuOx 9.748 14.2 90 1349.3376
PrBaCuOx 10.04 14.76 90 1487.8316
Nd BaCuOx 9.92 16 90 1574.5024
GdBaCuOx 9.75 15 90 1425.9375
DyBaCuOx 9.76 14.8 90 1409.8125
Spectroscopic and Thermal Characterization 101
Fig. 5.1 X-ray Powder diffractogram of Y2 (C2O4)3. 14H2O
Table 5.2 X-ray powder diffraction data for Y2 (C2O4)3.14H2O crystals
Sl.No 2θ0 d(obs.) d(cal.) hkl I/Imax
1 13.822 6.4 0164 6.2219 2 111 10.2564
2 18.573 4.77349 4.77177 210 100
3 25.919 3.43485 3.46763 103 10.2564
4 31.076 2.87554 2.87606 312 7.69230
5 32.222 2.77583 2.75000 004 20.513
6 34.818 2.57462 2.58372 114 12.8205
7 38.977 2.30894 2.30286 323 10.2564
8 39.767 2.26486 2.28717 332 12.8205
9 47.605 1.90864 1.90444 225 14.1026
10 61.269 1.51170 1.51622 515 12.8205
11 64.772 1.43815 1.43196 445 15.6
102 Chapter 5
Fig. 5.2 X-ray Powder diffractogram of Y2Ba (C2O4)4.8H2O crystals
Table 5.3 X-ray powder diffraction data for Y2Ba (C2O4)4.8H2O crystals
Sl.No 2θ(0) d (obs.) d (cal) h k l I/Imax
1 11.178 7.90922 7.9525 1 0 1 10.4167
2 12.456 7.10065 7.14178 110 100
3 18.705 4.73995 4.70251 2 0 1 14.5863
4 24.788 3.58888 3.57089 220 25
5 37.392 2.40309 2.40660 4 11 8.3
Spectroscopic and Thermal Characterization 103
Fig.5.3 X-ray Powder diffractogram of Y2BaCu (C2O4)4.8 H2O crystals
Table 5.4 X-ray powder diffraction data for Y2BaCu(C2O4)5.8H2O crystals
Sl.No 2θ(0) d(obs.) d(cal.) h k l I/Imax
1 9.065 9.74763 9.7487 100 100
2 12.425 7.11801 7.1000 002 54.76
3 13.908 6.36214 6.20129 111 26.19048
4 17.984 4.92837 4.94579 112 19.04762
4 18.67 4.74900 4.7333 003 52.38095
5 24.767 3.59197 3.5500 004 47.6190
6 37.368 2.40457 2.40205 401 11.9048
7 44.402 2.03859 2.0671 333 11.9048
8 45.567 1.98915 1.97999 423 9.52381
9 47.383 1.91708 1.91188 5 10 14.2857
10 48.401 1.87911 1.85762 424 9.52381
104 Chapter 5
Fig. 5.4 X-ray Powder diffractogram of Pr2BaCu (C2O4)5. 9H2O crystals
Table 5.5 X-ray powder diffraction data for Pr2BaCu (C2O4)5 .9H2O crystals
Sl.No. d (observe) d (cal). 2θ(0) h k l I /Imax
1. 10.02019 10.040 8.818 100 24.359
2. 6.5541 6.3978 13.499 111 42.3077
3. 5.095024 5.0200 17.391 200 19.2308
4. 4.77756 4.75264 18.557 201 100
5. 4.23318 4.29566 20.967 211 15.3846
6 3.69976 3.69000 24.034 004 12.8205
7. 3.50820 3.51379 25.368 203 26.9231
8. 3.04433 3.04792 29.313 302 16.6667
9 2.77938 2.78460 32.180 320 15.3846
10. 2.60799 2.60531 34.358 322 16.6667
11. 2.32223 2.32441 38.358 116 24.359
12.. 2.18111 2.18239 41.363 305 12.8205
13 2.04045 2.04243 44.36 423 20.5128
14.. 1.95623 1.95172 46.378 511 19.2308
Spectroscopic and Thermal Characterization 105
Fig. 5.5 X-ray Powder diffractogram of Nd2BaCu (C2O4)5 12 H2O crystals
Table 5.6 X-ray powder diffraction data for Nd2BaCu (C2O4)5.12H2O crystals
Sl.No 2θ 0 d(obs.)Å d(cal.)Å hkl I/Imax
1. 8.905 9.92284 9.92000 100 15.490
2. 13.680 6.46771 6.42425 111 23.944
3. 18.617 4.76227 4.7376 201 100
4. 25.583 3.4792 3.47474 114 19.7183
5. 30.361 2.94167 2.9304 223 11.2676
6. 33.127 2.70207 2.70393 313 14.0845
7. 48.225 1.88556 1.8879 335 25.3521
8. 68.920 1.36136 1.36262 720 24.6479
106 Chapter 5
Fig.5.6 X-ray Powder diffractogram of Gd2BaCu(C2O4)5.13 H2O crystals
Table 5.7 X-ray powder diffraction data for Gd2BaCu (C2O4)5.13 H2O crystals
Sl.No 2θ 0 d (obs.)Å d (cal.)Å hkl I/Imax
1. 9.052 9.76153 9.7500 100 34.6154
2. 12.973 6.8186 6.89429 110 23.0769
3. 13.860 6.38402 6.26430 111 30.7692
4. 17.886 4.9551 4.87500 200 23.0769
5. 18.690 4.74390 4.63629 201 100
6. 29.454 3.03017 3.02008 311 43.5897
7. 34.805 2.57556 2.54386 322 26.9230
8. 38.987 2.30835 2.31815 402 32.0513
9. 45.156 2.0063 2.0086 325 29.4872
Spectroscopic and Thermal Characterization 107
Fig.5.7 X-ray Powder diffractogram of Dy2BaCu (C2O4)5. 12 H2O crystals
Table 5.8 X-ray powder diffraction data for Dy2BaCu(C2O4)5. 12 H2O crystals
Sl.No 2θ 0 d(obs.)Å d(cal.)Å hkl I/Imax
1. 9.052 9.76192 9.7600 1 0 0 100
2. 13.740 6.43974 6.25476 11 1 29.78
3. 18.615 4.76283 4.63456 2 0 1 68.085
4. 26.908 3.31079 3.36055 2 2 1 29.78
5. 32.713 2.73531 2.71594 3 0 3 36.73
6. 38.930 2.31162 2.31728 4 0 2 29.78
108 Chapter 5
5.3 Analysis Infrared
The infrared absorption studies are an important tool in the
investigation of the molecular structure of crystals. Infra red radiation
promotes transitions in a molecule between rotational and vibrational energy
levels of the ground electronic energy states. It gives information about certain
group of atoms or functional groups present in the material. It was observed in
the present investigation that all the grown crystals showed almost identical
vibrationl modes and some have slight shift, which can be attributed to the
presence of constituent Rare Earth, Barium and Copper elements.
The FT-IR spectra of the crystalline samples of grown crystals were
recorded using KBr pellet method by Thermo-Nicolet Avator 370 in the
spectral range of 400cm-1 _ 4000cm-1.
5. 3 (a) IR spectrum of Yttrium Oxalate crystal
Fig.5.8. IR absorption spectrum of YOx crystals
Spectroscopic and Thermal Characterization 109
The IR absorption spectrum of (YOx) crystal is shown in Fig.5.8.
The stretching vibration of water molecules is expected in the region 3000-
3600 cm-1. The broad and sharp band at 3357cm-1 established the presence of
water of crystallization in the sample and was assigned to symmetric and
asymmetric stretching modes of water molecules. The bending mode of
water which is to be expected around 1630cm-1 and the asymmetric
stretching mode of oxalate ion which is expected at 1615cm-1 is overlapped
here to give the very strong peak at 1635.32cm-1.The considerable shift in
frequencies of stretching and bending modes from the free state values3
indicated the presence of hydrogen bonds of medium strengths4. On the basis
of the results available in the literature the very strong peaks at 1321.31cm-1
and weak one at 1364.05 cm-1 were identified as symmetric stretching modes
of CO2 group. The medium band at 490.54 cm-1 and weak one at 618.79 cm-1
were assigned as CO2 wagging modes. The strong band observed at
803.32cm-1 in the spectrum corresponds to the in plane deformation mode of
CO2. The peak at 1364.05cm-1 is assigned as due to symmetric stretching
mode of CO2 or the combinations of the neighbours.5
Extensive IR absorption studies of metallic oxalates 6, 7 proposed that
bands around 800cm-1 and 500cm-1 are due to metal-oxygen bond. The bands
observed at 490.54 cm-1 and 803.32 cm-1 may be considered as overlapping
110 Chapter 5
of metal oxygen bands with modes of oxalate ions. Infrared spectra of rare
earth oxalate crystals are given in the figures 5.8 – 5.15 and IR Spectra data
and vibrational assignments of rare earth oxalate crystals are given in the
tables 5.9 - 5.16 respectively.
Table5.9. IR Spectra data and vibrational assignments of YOx crystal
Wave number cm-1 Intensity Assignment
3357 s/b H2O stretching(sy&asy)
1635.32 v s H-O-H bending /CO2 asy. stretching
1321.31 s CO2 sy.stretching
1364.05 w Combinations
490.54 m CO2 Wagging / M-O bond
618.79 w CO2 Wagging
803.32 s CO2 in plane bend / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
Spectroscopic and Thermal Characterization 111
5. 3 (b) IR spectrum of Yttrium Barium Oxalate crystals
Fig.5.9. IR absorption spectrum of YBaOx crystals
Table 5.10 IR Spectra data and vibrational assignments of YBaOx crystal
Wave number cm-1 Intensity Assignment
3428.54 s/b H2O stretching (sy&asy)
1634.56 v s H-O-H bending / CO2 Asy. stretching
1356.19 w Combinations
1319.25 s CO2 sy.stretching
806.69 s CO2 in plane bend/ M-O bond
743.25 w Combinations
600.23 w CO2 Wagging
493.22 m CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
112 Chapter 5
5.3 (c) IR spectrum of Yttrium Copper Oxalate crystals
Fig.5.10 IR absorption spectrum of YCuOx crystals
Table5.11. IR Spectra data and vibrational assignments of YCuOx crystals
Wave number cm-1 Intensity Assignment
3399.68 s/b H2O stretching (sy&asy)
1631.66 v s H-O-H bending / CO2 asy. stretching
1363.57 w Combinations
1320 s CO2 sy.stretching
809.04 m CO2 in plane bend / M-O bond
605.24 w CO2 Wagging
490.84 m CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
Spectroscopic and Thermal Characterization 113
5.3 (d) IR spectrum of Yttrium Barium Copper Oxalate crystals
Fig.5.11 IR absorption spectrum of YBaCuOx crystals
Table 5.12. IR Spectra data and vibrational assignments of YBaCuOx crystals
Wave number cm-1 Intensity Assignment
3442.37 s/b H2O stretching (sy&asy)
1642.53 v s H-O-H bending / CO2 asy. Stretching
1362.72 w Combinations
1321.63 s CO2 sy.stretching
914.87 w Combinations
865.83 w Combinations
811.13 s CO2 in plane bend / M-O Bond
598.82 w CO2 Wagging
494.61 m CO2 Wagging / M-O bond
s-strong ,vs-very strong, m-medium, w-weak, v w-very weak b-broad
114 Chapter 5
5.3 (e). IR spectrum of Praseodymium Barium Copper Oxalate crystals
Fig.5.12 IR absorption spectrum of PrBaCuOx crystals
Table 5.13 IR Spectra data and vibrational assignments of PrBaCuOx crystals
Wave number cm-1 Intensity Assignment
3350.23 s/b H2O stretching (sy&asy)
1616.08 v s H-O-H bending / CO2 Asy. Stretching
1361.45 w Combinations
1316.96 s CO2 sy.stretching
799.25 m CO2 in plane bend / M-O bond
740.06 w Combinations
587.97 w CO2 Wagging
492.68 m CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
Spectroscopic and Thermal Characterization 115
5.3 (f) IR spectrum of Neodymium Barium Copper Oxalate crystals
Fig.5.13 IR absorption spectrum of NdBaCuOx crystals
Table5.14 IR Spectra data and vibrational assignments of NdBaCuOx crystals
Wave number cm-1 Intensity Assignment
3339.75 s/b H2O stretching (sy&asy)
2602.5 w Combination
2516.69 w Combination
1605.18 vs H-O-H bending / CO2 Asy. Stretching
1361.08 w Combination
1318.20 s CO2 sy.stretching
800.25 m CO2 in plane bend / M-O bond
490.31 m CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
116 Chapter 5
5.3 (g) IR spectrum of Gadolinium Barium Copper Oxalate crystals
Fig.5.14 IR absorption spectrum of GdBaCuOx crystals
Table 5.15. IR Spectra data and vibrational assignments of GdBaCuOx crystals
Wave number cm-1 Intensity Assignment
3336.32 s/b H2O stretching(sy&asy)
2614.76 w Combination
2533.03 w Combination
1616.34 vs H-O-H bending / CO2 Asy. stretching
1364.36 w Combination
1318.21 m CO2 sy.stretching
804.54 w CO2 in plane bend / M-O bond
484.84 m CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
Spectroscopic and Thermal Characterization 117
5.3 (h) IR spectrum of Dysprosium Barium Copper Oxalate crystals
Fig.5.15 IR absorption spectrum of DyBaCuOx crystal
Table 5.16. IR Spectra data and vibrational assignments of DyBaCuOx crystals
Wave number cm-1 Intensity Assignment
3338.15 s/b H2O stretching(sy&asy)
1624.04 vs H-O-H bending / CO2 Asy. stretching
1362.66 w Combination
1317.81 s CO2 sy.stretching
803.21 m CO2 in plane bend / M-O bond
488.50 s CO2 Wagging / M-O bond
s-strong, vs-very strong, m-medium, w-weak, v w-very weak b-broad
118 Chapter 5
5.4 Analysis Using Inductively Coupled Plasma Atomic Emission Spectrometer (ICP –AES)
The atomic spectrums emitted by the samples were used to
determine its elemental composition in Inductively Coupled Plasma Atomic
Emission Spectrometer. The wavelength at which emission occurs
identifies the element, quantifies its concentration. The results of the
analysis is given in the Tables 5.17.
Table5.17. Elemental composition of crystals
Concentration ratios R:Ba:Cu (R =Y, Pr, Dy, Gd) Elements
In feed solution Experimental
YBaCuOx 3.3: 1: 1 3.27: .996: .992
PrBaCuOx 3.3: 1: 1. 3.187: 1.05: .990
DyBaCuOx 3.3: 1: 1 3.538: 1.04: .958
GdBaCuOx 3.3: 1: 1 3.22: 1.037: .9626
5.5 Energy dispersive X-ray analysis
Energy dispersive X-ray analysis (EDAX) of the crystals confirmed
the presence of Rare Earth ions, Barium and Copper in the grown crystals.
In EDAX the sample is irradiated with high-energy electrons. The energy
of the radiations emitted by the specimen is related to the number of atoms
Spectroscopic and Thermal Characterization 119
of the elements present in the sample. EDAX spectrogram is a curve
plotted between binding energy and the intensity of emitted photoelectron.
The peak heights or areas are a measure of the quantity of the concerned
elements incorporated in the specimen. Though not very accurate, the
comparison of the EDAX peaks of the two elements in a sample gives an
approximate proportion of the elements.
EDAX analyser No. 711, an accessory to the scanning electron
microscope, Philips SEM model 501 was used for the EDAX analysis of
the sample. In the present study each sample was finely powdered and
pellets of 1cm diameter and 1mm thickness were formed using a hydraulic
press by applying pressure of 1.1 ton per cm2. For EDAX, the pellet was
mounted onto an aluminium stub and the surface of the pellet was coated
with gold so as to make good electrical conduction.
120 Chapter 5
5.5.1 EDAX of NdBaCuOx Crystals
The NdBaCuOx crystals were grown by diffusion of 1M solution of
Neodymium Chloride, 0.3M solution of Barium Chloride and 0.3M
solution of Cuprous Nitrate in equal proportion by volume through a gel
column impregnated with 1M Oxalic acid were selected for the
investigation. The EDAX pattern obtained NdBaCuOx crystal is as shown
in the figure 5.16. The elemental incorporation of Nd, Ba and Cu in the
given samples is evident from peaks for these elements. The three peaks
positioned at 5.0 keV, 5.25 keV and 8.01 keV relates to the presence of
Barium, Neodymium and Copper respectively.
Fig 5.16 EDAX pattern of NdBaCuOx
Spectroscopic and Thermal Characterization 121
5.5.2 EDAX of YBaCuOx Crystals
The YBaCuOx crystals were grown by gel method. EDAX pattern of
YBaCuOx crystals was taken and it is shown in the Fig.5.17. The elemental
incorporation of Y, Ba and Cu in the given sample is evident from peaks for
these elements. The three peaks positioned at 2 keV, 5.01 keV and 8.02 keV
relates to the presence of Yttrium, Barium and Copper respectively.
Fig. 5.17 EDAX pattern of YBaCuOx
122 Chapter 5
5.6 THERMAL ANALYSIS
The thermal characteristics of the grown crystals were studied using
Perkin Elmer, Diamond TG/DTA. The temperature range selected for the
present study was from ambient temperature to 12000C.
5.6.1 TG / DTA of Yttrium Oxalate Crystals
Fig.5.18 TG /DTA of YOx crystals
Fig.5.18 shows the TG /DTA curve for Yttrium Oxalate Crystals
with chemical formula Y2 (C2O4)3.14 H2O. The thermogram depicts the
decomposition stages of Y2 (C2O4)3.14 H2O crystal with temperature.
Taking the initial weight as standard, the course of decomposition is
analyzed from proportionate weight loss at each stage. The material
started decomposing at about 26.44 0C and the process was completed at
Spectroscopic and Thermal Characterization 123
about 5000C at which it is reduced to oxide form. The process of
decomposition involved two very distinct stages. The first stage, which
extends up to 1800C is a dehydration stage and results in the elimination
of all the fourteen water molecules. An endothermic peak centered at
1000C characterizes this. The anhydrous Y2 (C2O4) 3 is unstable and
decomposes during the second stage. The loss of weight around 4320C is
due to two chemical stages; one is related to the release of three CO2
molecules in the temperature range 1800C – 4320C and the other related to
the release of three CO molecules in the temperature range 4320C ─
5000C. At the end of the second stage the sample is reduced to Y2O3, the
corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can
be assumed as follows.
20 0
-14H O2 2 4 3 2 2 2 4 326.44 C-180 C
Y (C O ) 14H O Y (C O )→
20 0
-(3CO+3CO )2 2 4 3 2 3180 C-500 C
Y (C O ) Y O→
Results of thermal analysis are given in table 5.18. The observed
mass loss and calculated mass loss in both stages are tallied.
124 Chapter 5
Table 5.18. Thermal analysis results of Y2 (C2O4)3.14H2O crystals
Decomposition
Temp. 0C
Loss of
material Observed
mass loss % Calculated
mass loss % Nature of
reaction
26.44 -180 14 H2O 36.3700 36.3210 Endo dehydration
180 -500 3CO2+3CO 31.0080 31.1320 Endo decomposition
5.6.2 TG / DTA of Yttrium Barium Oxalate Crystals.
Fig.5.19 TG /DTA of YBaOx crystals
Fig. 5.19 shows the TG /DTA curve for Yttrium Barium Oxalate
Crystals with chemical formula Y2Ba (C2O4)4.8H2O. The thermogram
depicts the decomposition stages of crystal Y2Ba (C2O4)4. 8H2O with
temperature. Taking the initial weight as standard, the course of
Spectroscopic and Thermal Characterization 125
decomposition is analyzed from proportionate weight loss at each stage.
The material started decomposing at about 38.08 0C and the process was
completed at about 5000C at which it was reduced to oxide form. The
process of decomposition involves two very distinct stages. The first stage,
which extends up to 116.420C is a dehydration stage and results in the
elimination of all the eight water molecules. An endothermic peak centered
at 92.210C characterizes this. The anhydrous Y2Ba (C2O4)4 is unstable and
decomposes during the second stage. The loss of weight around 434.050C is
due to two chemical stages, one is related to the release of four CO
molecules in the temperature range 116.420C – 421.230C and the other
related to the release of four CO2 molecules in the temperature range
421.230–5000C that are endothermic in character with endothermic peaks
centered at 421.230C and 434.050C respectively. At the end of the second
stage the sample is reduced to Y2BaO4, the corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can
be assumed as follows.
20 0-8H O
2 2 4 4 2 2 2 4 438.08 C-116.42 CY Ba(C O ) 8H O Y Ba(C O )→
2
0 0-(4CO+4CO )
2 2 4 4 2 2 4 4116.42 C - 500 CY Ba(C O ) Y Ba(C O )→
126 Chapter 5
Results of thermal analysis are given in table 5.19. The observed
mass loss and calculated mass loss in both stages are tallied.
Table 5.19. Thermal analysis results of Y2Ba (C2O4)4. 8H2O crystals
Decomposition Temp.0C
Loss of material
Observed mass loss %
Calculated mass loss %
Nature of reaction
38.08 -116.42 8 H2O 16.7358 17.7520 Endo dehydration
116.42 -500 4CO2+4CO 35.3840 35.5047 Endo
decomposition
5.6.3 TG / DTA of Yttrium Copper Oxalate Crystals.
Fig.5.20 TG /DTA of YCuOx crystals
Fig.5.20 shows the TG /DTA curve for Yttrium Copper Oxalate
Crystals with chemical formula Y2Cu (C2O4)4.7 H2O. The thermogram
Spectroscopic and Thermal Characterization 127
depicts the decomposition stages of crystal Y2Cu (C2O4)4.7 H2O with
temperature. Taking the initial weight as standard, the course of
decomposition was analyzed from proportionate weight loss at each stage.
The material started decomposing at about 35.830C and the process was
completed at about 533.330C at which it was reduced to oxide form. The
process of decomposition involves two very distinct stages. The first stage,
which extends up to 100.780C is a dehydration stage and results in the
limination of all the seven water molecules. An endothermic peak centered
at 100.780C characterizes this. The anhydrous Y2Cu (C2O4)4 is unstable and
decomposes during the second stage. The loss of weight around 434.59 0C
is due to two chemical stages, one is related to the release of four CO
molecules in the temperature range 100.78 0C – 416.67 0C and the other
related to the release of four CO2 molecules 416.67 0C – 533.34 0C. At the
end of the second stage the sample is reduced to Y2CuO4, the
corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can be
assumed as follows.
20 0-7 H O
2 2 4 4. 2 2 2 4 435.83 C - 100.75 CY Cu(C O ) 7H O ( )Y Cu C O→
20 0
-(4CO+4CO )2 2 4 4 2 4100.75 C-533.34 C
Y Cu (C O ) Y CuO→
128 Chapter 5
Results of thermal analysis are given in table 5.20. The observed
mass loss and calculated mass loss in both stages show only a slight
difference.
Table 5.20. Thermal analysis results of Y2 Cu (C2O4)4.7 H2O crystals
Decomposition Temp. 0C
Loss of material
Observed mass loss %
Calculated mass loss %
Nature of reaction
35.83 -100.78 7 H2O 17.5153 16.6378 Endo dehydration
100.78 -533.34 4CO2+4CO 40.0350 39.999 Endo
decomposition
5.6.4 TG / DTA of Yttrium Barium Copper Oxalate Crystals.
Fig.5.21 TG /DTA of YBaCuOx crystals
Spectroscopic and Thermal Characterization 129
Fig.5.21 shows the TG /DTA curve for Yttrium Barium Copper
Oxalate Crystals with chemical formula Y2BaCu(C2O4)5.8H2O. The
thermogram depicts the decomposition stages of crystal
Y2BaCu(C2O4)5.8H2O with temperature. Taking the initial weight as
standard, the course of decomposition was analyzed from proportionate
weight loss at each stage. The material started decomposing at about
35.980C and the process was completed at about 5360C at which it was
reduced to oxide form. The process of decomposition involves two very
distinct stages. The first stage, which extends up to 1210C is a dehydration
stage and results in the elimination of all the eight water molecules. This is
characterized by an endothermic peak centered at 108.370C. The anhydrous
Y2BaCu (C2O4)5 is unstable and decomposes during the second stage. The
loss of weight around 5000C is due to two chemical stages, one is related to
the release of five CO molecules in the temperature range 1210C – 4010C
and the other related to the release of five CO2 molecules in the temperature
range 4010C – 5360C. At the end of the second stage the sample is reduced
toY2BaCuO5, the corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can be
assumed as follows.
130 Chapter 5
20 0
-8 H O2 2 4 5. 2 2 2 4 535.98 C - 121 C
Y BaCu(C O ) 8H O Y BaCu(C O )→
20 0
-(5 CO+5CO )2 2 4 5 2 5121 C - 536 C
Y BaCu(C O ) Y BaCuO→
Results of thermal analysis are given in table 5.21. The observed
mass loss and calculated mass loss in both stages are tallied.
Table 5.21. Thermal analysis results of Y2BaCu (C2O4)5 .8H2O crystals
Decomposition
Temp. 0C
Loss of
Material
Observed mass loss
%
Calculated mass loss %
Nature of reaction
35.98 - 121 8 H2O 14.9950 14.9500 Endo dehydration
121 - 536 5CO2+5CO 37.7750 37.3940 Endo decomposition
5.6.5 TG / DTA of Praseodymium Barium Copper Oxalate Crystals.
Fig.5.22 TG /DTA of Pr BaCuOx crystals
Spectroscopic and Thermal Characterization 131
Fig.5.22 shows the TG /DTA curve for Praseodymium Barium
Copper Oxalate Crystals with chemical formula Pr2BaCu(C2O4)5.9H2O. The
thermogram depicts the decomposition stages of crystal Pr2BaCu(C2O4)5.9H2O
with temperature. Taking the initial weight as standard, the course of
decomposition is analyzed from proportionate weight loss at each stage. The
material started decomposing at about 45.740C and the process was completed at
about 5700C at which it was reduced to oxide form. The process of
decomposition involves two very distinct stages. The first stage, which extends
up to 1250C is a dehydration stage and results in the elimination of all the nine
water molecules. An endothermic peak centered at 124.560C characterizes this.
The anhydrous Pr2BaCu (C2O4)5 is unstable and decomposes during the second
stage. Loss of weight in the temperature range 1250C– 5700C relates to the
release of five molecules of CO and CO2 that is endothermic in character with
endothermic peak centered at 564.52 0C. At the end of the second stage the
sample is reduced to Pr2BaCuO5, the corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can be
assumed as follows.
20 0
-9 H O2 2 4 5. 2 2 2 4 545.74 C - 125 C
Y BaCu(C O ) 9H O Y BaCu(C O )→
20 0
-(5CO+5CO )2 2 4 5 2 5125 C - 270 C
Pr BaCu(C O ) Pr BaCuCuO→
132 Chapter 5
Results of thermal analysis are given in table 5.22. The observed
mass loss and calculated mass loss in both stages show only a slight
difference.
Table 5.22. Thermal analysis results of Pr2BaCu (C2O4)5.9 H2O crystals
Decomposition Temp. 0C
Loss of material
Observed mass loss %
Calculated mass loss %
Nature of reaction
45.74 -125 9H2O 15.4369 14.9349 Endo dehydration
125 - 570 5CO2+5CO 35.8351 33.1886 Endo decomposition
5.6.6 TG / DTA of Neodymium Barium Copper Oxalate Crystals.
Fig.5.23 TG /DTA of NdBaCuOx crystals
Spectroscopic and Thermal Characterization 133
Fig.5.23 shows the TG /DTA curve for Neodymium Barium Copper
Oxalate Crystals with chemical formula Nd2BaCu (C2O4)5.12 H2O. The
thermogram depicts the decomposition stages of crystal, Nd2BaCu
(C2O4)5.12H2O with temperature. Taking the initial weight as standard, the
course of decomposition was analyzed from proportionate weight loss at
each stage. The material started decomposing at about 39.57 0C and the
process was completed at about 7150C at which it was reduced to oxide
form. The process of decomposition involves two very distinct stages. The
first stage, which extends up to 2050C is a dehydration stage and results in
the elimination of all the twelve molecules of water. The loss of weight
around 2050C is due to two chemical stages; one is related to the release of
nine molecules of water in the temperature range.
39.570C -1500C and the other related to the release of three
molecules of water in the temperature range 1500C – 2050C. Endothermic
peaks centered at 112.910C and at 204.950C respectively characterize these.
The anhydrous Nd2BaCu (C2O4)5 unstable and decomposes during the
second stage. The loss of weight around 4100C is due to two chemical
stages, one is related to the release of five CO molecules in the temperature
range 2050C - 4200C and the other related to the release of five CO2
134 Chapter 5
molecules 4200C - 7150C. At the end of the second stage the sample is
reduced toNd2BaCuO5, the corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can be
assumed as follows.
20 0
-12 H O2 2 4 5 2 2 2 4 539.57 C -205 C
Nd BaCu (C O ) .12 H O Nd BaCu (C O )→
20 0
- (5CO+5CO )2 2 4 5 2 5205 C - 715 C
Nd BaCu (C O ) Nd BaCuO→
Results of thermal analysis are given in table 5.23. The observed
mass loss and calculated mass loss in both stages show only a slight
difference.
Table 5.23.Thermal analysis results of Nd2BaCu (C2O4)5.12 H2O crystals
Decomposition Temp. 0C
Loss of material
Observed mass loss %
Calculated mass loss %
Nature of reaction
39.57 - 205 12H2O 18.9201 18.8589 Endo dehydration
205 - 715 5CO2+5CO 31.6620 36.1188 Endo decomposition
Spectroscopic and Thermal Characterization 135
5.6.7 TG / DTA of Gadolinium Barium Copper Oxalate Crystals.
Fig.5.24 TG /DTA of GdBaCuOx crystals
Fig.5.24 shows the TG /DTA curve for Gadolinium Barium
Copper Oxalate Crystals with chemical formula Gd2BaCu(C2O4)5.13H2O.
The thermogram depicts the decomposition stages of crystal Gd2BaCu
(C2O4)5.13 H2O with temperature. Taking the initial weight as standard,
the course of decomposition was analyzed from proportionate weight loss
at each stage. The material started decomposing at about 39.370C and the
process was completed at about 8150C at which it was reduced to oxide
form. The process of decomposition involves two very distinct stages.
The first stage, which extends up to 2350C is a dehydration stage and
results in the elimination of all the thirteen water molecules. Endothermic
136 Chapter 5
peaks centered at 91.190C and at 218.020C characterize this. The
anhydrous Gd2BaCu (C2O4)5 is unstable and decomposes during the
second stage. The second stage, which extends up to 8150C is a
decomposition stage and results in the elimination of five molecules of
CO and five molecules of CO2 in the temperature range 2350C – 815 0C.
At the end of the second stage the sample is reduced to Gd2BaCuO5, the
corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can
be assumed as follows
20 0
-13H O2 2 4 5 2 2 2 4 539.37 C -235 C
Gd BaCu (C O ) .13 H O Gd BaCu (C O )→
20 0
- (5CO+5CO )2 2 4 5 2 5235 C - 815 C
Gd BaCu (C O ) Gd BaCuO→
Results of thermal analysis are given in table 5.24. The observed
mass loss and calculated mass loss in both stages are tallied.
Spectroscopic and Thermal Characterization 137
Table 5.24. Thermal analysis results of Gd2BaCu (C2O4)5.13 H2O crystals
Decomposition Temp. 0C
Loss of material
Observed mass loss
%
Calculated mass loss %
Nature of reaction
39.37 - 235 13 H2O 19.6360 19.6740 Endo dehydration
235 –815 5CO2+5CO 30.9670 30.2676 Endo
decomposition
5.6.8 TG / DTA of Dysprosium Barium Copper Oxalate Crystals.
Fig.5.25 TG /DTA of DyBaCuOx crystals
Fig.5.25 shows the TG /DTA curve for Dysprosium Barium Copper
Oxalate Crystals with chemical formula Dy2BaCu(C2O4)5.12H2O. The
thermogram depicts the decomposition stages of crystal Dy2BaCu
138 Chapter 5
(C2O4)5.12 H2O with temperature. Taking the initial weight as standard, the
course of decomposition was analyzed from proportionate weight loss at
each stage. The material started decomposing at about 39.54 0C and the
process was completed at about 7800C at which it was reduced to oxide
form. The process of decomposition involves two very distinct stages. The
first stage, which extends up to 2050C is a dehydration stage and results in
the elimination of all the twelve water molecules. Endothermic peaks
centered at 85.890C and 177.240C characterize this. The anhydrous Dy2BaCu
(C2O4)5 is unstable and decomposes during the second stage. The second
stage which extends up to 7800C is a decomposition stage and results in the
elimination of five molecules of CO and five molecules of CO2 in the
temperature range 2050C – 7800C. At the end of the second stage the sample
is reduced to Dy2BaCuO5, the corresponding rare earth oxide.
The thermal decomposition mechanism of the grown samples can be
assumed as follows
20 0
-12 H O2 2 4 5 2 2 4 539.54 C -205 C
Dy BaCu (C O ) .12 H2O Dy BaCu (C O ) →
20 0
- (5CO+5CO )2 2 4 5 2 5205 C -780 C
Dy BaCu (C O ) Dy BaCuO →
Spectroscopic and Thermal Characterization 139
Results of thermal analysis are given in table 5.25. The observed
mass loss and calculated mass loss in both stages show only a slight
difference.
Table 5.25. Thermal analysis results of Dy2BaCu (C2O4)5.12 H2O crystals
Decomposition Temp. 0C
Loss of material
Observed mass loss %
Calculated mass loss %
Nature of reaction
39.54 -205 12 H2O 17.9530 18.2760 Endo dehydration
205 -780 5CO2+5CO 30.4105 30.4597 Endo
decomposition
5.7 Differential scanning calorimetry (DSC)
Differential scanning calorimetry (DSC) is a thermoanalytical
technique in which the difference in the amount of heat required to increase
the temperature of a sample and reference are measured as a function of
temperature. In the present study DSC curve was recorded by using Mettler
Toledo DSC 822e.at the sampling rate of Max 10 values /sec in the
temperature range of -150 0C to7000C. DSC measures the amount of heat
energy absorbed or released by a sample, as it is heated or cooled or held at
constant temperature. For DSC analysis, Non – explosive, non –corrosive
samples, about 10–50 mg are required.
140 Chapter 5
5.7.1 DSC Analysis of Yttrium Oxalate Crystals
Fig.5.26. DSC analysis of YOx crystals
Fig.5.26 shows the DSC curve for Yttrium Oxalate Crystals with
chemical formula Y2 (C2O4)3.14 H2O. The curve depicts the decomposition
stages of Y2 (C2O4)3.14 H2O crystals with temperature. The endothermic
peak at 133.360 C relates to the loss of water of crystallization and
endothermic peak at 434.430 C is characterized due to the release of CO
and CO2.
Spectroscopic and Thermal Characterization 141
57.2 DSC Analysis of Yttrium Barium Oxalate Crystals
Fig.5.27. DSC analysis of YBaOx crystals
Fig.5.27 shows the DSC curve for Yttrium Barium Oxalate Crystals
with chemical formula Y2Ba(C2O4)4.8H2O. The curve depicts the
decomposition stages of Y2Ba (C2O4)4.8H2O crystals with temperature. The
endothermic peak at 110.700C relates to the loss of water of crystallization
and endothermic peaks at 240.390C, 371.520 C and 435.960 C are due to the
release of four molecules of CO and four molecules of CO2.
142 Chapter 5
5.7.3 DSC Analysis of Yttrium Copper Oxalate Crystals
Fig.5.28. DSC analysis of YCuOx crystals
Fig.5.28 shows the DSC curve for Yttrium Copper Oxalate Crystals
with chemical formula Y2Cu(C2O4)4.7H2O. The curve depicts the
decomposition stages of Y2Cu(C2O4)4.7H2O crystals with temperature. The
endothermic peak at 102.730C relates to the loss of water of crystallization
and endothermic peaks at 177.930C, 360.400C and 425.600C are due to the
release of four molecules of CO and four molecules of CO2.
Spectroscopic and Thermal Characterization 143
5.7.4 DSC Analysis Of Yttrium Barium Copper Oxalate Crystals
Fig.5.29 DSC analysis of YBaCuOx crystals
Fig.5.29 shows the DSC curve for Yttrium Barium Copper Oxalate
Crystals with chemical formula Y2BaCu(C2O4)5.8H2O. The curve depicts
the decomposition stages of Y2BaCu(C2O4)5.8H2O crystals with
temperature. The endothermic peak at 102.730C relates to the loss of
water of crystallization and endothermic peaks at 227.520C, 433.550C and
523.750C are due to the release of five molecules of CO and five
molecules of CO2.
144 Chapter 5
5.7.5 DSC Analysis of Praseodymium Barium Copper Oxalate Crystals
Fig.5.30 DSC analysis of PrBaCuOx crystals
Fig.5.30 shows the DSC curve for Praseodymium Barium Copper
Oxalate Crystals with chemical formula Pr2BaCu(C2O4)5.9 H2O. The curve
depicts the decomposition stages of Pr2BaCu(C2O4)5.9H2O crystals with
temperature. The endothermic peak at 163.390C relates to the loss of water
of crystallization and endothermic peaks at 224.97 0Cand 402.58 0C are due
to the release of five molecules of CO and five molecules of CO2.
Spectroscopic and Thermal Characterization 145
5.7.6 DSC Analysis of Neodymium Barium Copper Oxalate Crystals
Fig.5.31 DSC analysis of NdBaCuOx crystals
Fig.5.31 shows the DSC curve for Neodymium Barium Copper
Oxalate Crystals with chemical formula Nd2BaCu(C2O4)5.12H2O. The
curve depicts the decomposition stages of Nd2BaCu(C2O4)5.12H2O crystals
with temperature. The endothermic peaks at 1480C and 174.170C relate to
the loss of twelve molecules of water. The endothermic peaks at 261.190C
and 408.39 0C are due to the release of five molecules of CO and five
molecules of CO2.
146 Chapter 5
5.7.7 DSC Analysis of Gadolinium Barium Copper Oxalate Crystals
Fig.5.32 DSC analysis of GdBaCuOx crystals
Fig.5.32 shows the DSC curve for Gadolinium Barium Copper
Oxalate Crystals with chemical formula Gd2BaCu(C2O4)5.13H2O. The
curve depicts the decomposition stages of Gd2BaCu(C2O4)5.13H2O crystals
with temperature. The endothermic peaks at 134.13 0C and 197.14 0C relate
to the loss of thirteen molecules of water. The endothermic peaks at 275.35
0C and 434.63 0C are due to the release of five molecules of CO and five
molecules of CO2
Spectroscopic and Thermal Characterization 147
5.7.8 DSC Analysis of Dysprosium Barium Copper Oxalate Crystals
Fig.5.33 DSC analysis of DyBaCuOx crystals
Fig.5.33 shows the DSC curve for Dysprosium Barium Copper
Oxalate Crystals with chemical formula Dy2BaCu (C2O4)5.12H2O.. The
curve depicts the decomposition stages of Dy2BaCu(C2O4)5.12H2O crystals
with temperature. The endothermic peaks at 131.110C and 219.290C relate
to the loss of twelve molecules of water. The endothermic peaks at
266.030C, 365.400C and 434.520C are due to the release of five molecules
of CO and five molecules of CO2.
148 Chapter 5
5.8 CONCLUSION
X-ray powder diffraction analyses of the grown crystals provided
their lattice parameters. It was observed that all the grown crystals are in
the tetragonal system. FT-IR studies showed the presence of various
functional groups. IR studies confirmed the presence of water of
crystallization and oxalate group in the rare earth mixed oxalate crystals.
The thermal analysis data supported the structural formula for the rare earth
mixed oxalate crystals. DSC measured the amount of heat energy absorbed
or released by the rare earth mixed oxalate crystals, as it is heated, cooled
or held at a constant temperature. Complementary results were obtained
for decomposition and dehydration reactions in both TG/DTA and DSC
studies. Rare Earth, Barium and Copper in the samples were analysed by
Inductively Coupled Plasma Atomic Emission Spectrometer (ICP –AES)
and Energy Dispersive Analysis by X-rays (EDAX).
Spectroscopic and Thermal Characterization 149
5.9 REFERENCES
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2 Ollendorff W. and F. Weigel, Inorg. Nucl.Chem. Letters, 5 (1969) 263.
3 Mathew X., Suresh G., Pradeep T. and Nayer V. U., J. Raman
Spectroscopy, 21 (1990)279.
4 Vinogradov S. N. and Linnell R. H., Hydrogen Bonding, Von
Nostrand Rein hold, New York, 1971.
5 Petrosv I. and Soptrajanov B., Spectrochimica Acta, 31A(1975) 309.
6 Fujitha J., Martell A. E. and Nakamoto K. J.Chemical Physics , 36
(1962).
7 Gibson J.K. and N.A., Thermo chemical Acta, 226 (1993)301.
8 Wendlandt W.W., Thermal Methods of Analysis, 2 nd Edn. Wiley,
New York, 1974.
9 Mahadeo, A. Nabar and V. R. Ajgaokar., Less- Common Metals, 106
(1985)211.
10 Pope M.I., and Judd M. D., Differential Thermal Analysis, Hedyden,
Philadelphia, 1977.