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Transcript of URD poster
Electrodeposition of Lanthanum Thin Films
Yitzhak Snow, Tyler Pounds, Stephen Farias, Robert C. Cammarata, Jonah Erlebacher
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
INTRODUCTION:
We designed a system to electrochemically deposit smooth
lanthanum films from an ionic liquid.
Lanthanum compounds have a number of significant applications.
We demonstrate the first smooth electrochemically deposited
lanthanum film, although monocrystalline lanthanum films have
been reported [1].
Electrochemical deposition provides a scalable method to produce
conformal films at low processing temperatures. In addition, the
process allows for the synthesis of materials directly into a
nanostructured form, which could provide improved materials
performance [2].
We report electrochemical synthesis of La2O3 thin films, using ionic
liquid electrolytes to extend the potential window and minimize
oxidation of lanthanum during deposition. The reported
electrochemical deposition technique may also be a viable
processing technique for producing other lanthanum compounds.
RESULTS:
Through electrochemical deposition,
the bottom end of the wire was coated
in a film (Fig. 2,3,4). EDAX analysis
(Fig. 1, Table 1) determined the
elemental composition. Lanthanum
makes up 22.08% of the analyzed
specimen, by weight.
The bromine is present due to its
function as the anion in ionic liquid
that serves as the electrolyte, resulting
in high concentrations in the film. The
oxygen is present in part because
lanthanum reacts readily with air,
forming La2O3. The silver seen is the
substrate.
CONCLUSIONS :
This work has shown the feasibility of electrochemical
deposition to create thin films of lanthanum and lanthanum
compounds. This could allow for the creation of
thermoelectric and other materials with increased control over
the nanostructure. Although the lanthanum films are prone to
rapid oxidation, they have still been created using these
techniques.
In the future, increased control over oxygen and in the
electrochemical cell should allow for the creation of metallic
lanthanum, rather than an oxide. It remains to be determined at
what stage of the reaction the oxidation takes place.
In addition, addition of other ions to the electrolyte should
allow for their co-deposition with lanthanum, allowing for the
creation of lanthanum compounds.
By using a nanostructured aluminum oxide substrate as the
working electrode, electrochemical films can be manufactured
in a nanostructure quickly and simply. Nanostructured films of
lanthanum and lanthanum compounds could have improved
properties compared to the bulk material.
REFERENCES:
1. Legeai, S., Diliberto, S., Stein, N., Boulanger, C., Estager,
J., Papaiconomou, N., & Draye, M. (2008). Room-
temperature ionic liquid for lanthanum electrodeposition.
Electrochemistry Communications, 10(11), 1661-1664.
2. Chi, S. I. C., Farias, S. L., & Cammarata, R. C. (2013,
January). A Novel Approach to Synthesize Lanthanum
Telluride Thermoelectric Thin Films in Ambient
Conditions. In MRS Proceedings (Vol. 1543, pp. 113-118).
Cambridge University Press.
METHODS/ MATERIALS:
The goal was to design a system in which lanthanide films could be
electrochemically deposited. The ionic liquid, 1-ethyl-3-
methylimidazolium bromide (EMIM-Br), was prepared in house
according to the reaction scheme shown.
EDAX ZAF Quantification
(Standardless)
Element Normalized
SEC Table : Default
Element Wt % At %
Br L 39.84 16.7
La L 22.08 5.33
C K 18.92 52.76
Ag L 5.82 1.81
O K 5.12 10.73
N K 4.39 10.5
Ni L 3.82 2.18
Total 100 100
Table 1 EDAX analysis of film
Figure 1 EDAX peaks, showing the presence of lanthanum
SEM images of lanthanum oxide films electrochemically deposited on a silver
wire. Magnifications of;
250x (Figure 2, left, 500x (Figure 3, middle), 1000x (Figure 4, bottom)
ACKNOWLEDGEMENTS:
Johns Hopkins department of Materials Science and
Engineering
Hopkins Extreme Materials Institute
-8 E-04
-6 E-04
-4 E-04
-2 E-04
0 E+00
2 E-04
4 E-04
6 E-04
8 E-04
-4 E-04
-3 E-04
-2 E-04
-1 E-04
0 E+00
1 E-04
2 E-04
3 E-04
4 E-04
-2 -1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0
Curr
ent,
Liq
uid
wit
h n
o L
anth
anu
m (
amp
s)
Curr
ent,
Liq
uid
wit
h a
dd
ed L
anth
anu
m (
amp
s)
Voltage (volts)
Cyclic Voltammetry of Ionic Liquid Electrolyte
Ionic Liquid with 0.4g Lanthanum
Ionic Liquid with no Lanthanum
Figure 6 CV curves for IL with and without lanthanumFigure 5 Design of 3 electrode cell configuration
used to deposit the lanthanum films.
FUTURE WORK:
Although lanthanum films can be consistently deposited, the
primary problem with the current procedure is the constant
oxidation of the lanthanum films. To avoid this, more control
will be needed to eliminate water from the reaction
environment. This would mean the dehydration of the
lanthanum salt, complete drying of the ionic liquid, and better
control over the humidity in the atmosphere of the reaction
cell. All of these steps have been worked on in some capacity,
with varying degrees of success.
Mixed under Ar+
Ionic liquids are necessary for lanthanum deposition, because the in
an aqueous solution, the water would undergo electrolysis before
lanthanum ions would be reduced. In addition, the oxygen dissolved
in the water would immediately react with the lanthanum, since
lanthanum reacts spontaneously and rapidly with even small
quantities of oxygen. EMIM-Br has a low oxygen solubility and a
low melting temperature (~75° C). The ionic liquid was kept under
argon, beginning with the synthesis of the liquid, and continuing
through the addition and deposition of lanthanum. This was achieved
by blowing argon gas into the reaction cell at a positive pressure.
The ionic liquid was melted and kept at a constant 90° C using a
water bath, in the setup shown (Fig. 5).
Approximately 0.5 g of lanthanum nitrate hexahydrate, La(NO3)3,
was added to about 10 ml of the ionic liquid, where it separates into
La3+ and (NO3)-. A three electrode system was used, with a Ag/AgCl
reference electrode, a platinum counter electrode, and a silver wire
working electrode. Cyclic voltammetry (Fig. 6) determined the
presence of a deposition peak at approximately -1.5 volts with
respect to the reference. A potentiostatic deposition was then run for
five minutes at -1.5 volts with respect to the reference. Upon the
completion of the deposition, the wire was analyzed in an SEM
using LEI detection, with EDAX to characterize the elemental
composition.