Lu2Hf2O7 Sintering

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  • SENIOR DESIGN PROGRESS REPORT

    Sintering and Optical Properties of TransparentLu2Hf2O7 Scintillators

    Student Name: Kyle Crosby Harrison Deamon Mark Minchello

    Academic Advisor: Leon Shaw University of Connecticut (UConn)

    Industry Advisor: Edgar Van Loef Radiation Monitoring Devices (RMD)

    November 10, 2006

  • ObjectivesCreate a transparent ceramic from Lu2Hf2O7 powderTransparency results when solid is 99.99% of the theoretical density (no pores to deflect phonons)Theoretical density of Lu2Hf2O7 = 9.95 g/mLConfirm ideal cold pressing, sintering, and hot isostatic pressing (HIP) conditionsIf successful, these ceramics will be doped with Ce and used as scintillators.

  • Ceramic ScintillatorsDefinitionEmits light when excited by radiationTransparencyAllows photons to escapeStopping efficiencyAttenuation directly related to densityDopingIntermediate energy level for e- excitation

  • Phase DiagramHfO2 Lu2O3 Composition of powder

  • Uniaxial PressPellets at 450 MPaNon-uniform densificationLamellar cracking

    Pressed at 50 & 150 MPa w/ ethanol lubricantImproved handlingNo lamellar cracking.5 die

  • Sintering Mechanisms Particles after pressingPoint contact Pore formation and particle coalescenceNeck growthDensity < 70%Pore reductionDensification with closed spherical poresDensity > 92%

  • Graphite FurnaceSinter temperatures 1600C, 1700C, 1800C, 1900C, 2100CSinter cycle schedule0 - 1000 C45 minutes1000 - 1800 C10/minute1800 C 120 minute soak1800 - 1000 C20/minute1000 - 0 Cfree cooling

  • Furnace AtmosphereHeliumSmallest inert gas

    Argon Larger atomic radius

  • Sintering DifficultiesFurnace repairFilament replacement ReductionLoss of O2

  • Oxidation FurnaceOptimal conditions1400 C2 hour dwellNecessary procedureReintroduced O2

  • Characterization

    XRDContinuous spectrum analysisd-spacing to determine lattice parameter

    Optical MicroscopyMicrostructure examinationRelative degree of porosity, relative pore size

    SEMPowder particle size distributionSintering effects

  • X-Ray Diffraction (XRD)Bruker D50052.2 kW copper x-ray tubes

    Operation parameters40 kV & 40mA10-90 scan, .02 step size, 4 per minute

  • Powder Diffraction Pattern

    Chart1

    2.8611

    6.9861

    2.8194

    5.5556

    5.5972

    2.8194

    1.4722

    4.2083

    0.125

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    4.2083

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    0.125

    5.5556

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    2.8611

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    4.1667

    5.5972

    1.4722

    0.125

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    5.5972

    1.4722

    2.8194

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    1.4722

    4.25

    2.8611

    4.2083

    4.2083

    5.5556

    1.4722

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    0.125

    2.8611

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    4.1667

    1.4722

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    4.25

    2.8194

    4.2083

    5.5556

    0.125

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    4.2083

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    4.2083

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    5.5972

    6.9861

    2.8194

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    2.8611

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    6.9444

    4.25

    1.4722

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    2.8611

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    1.4722

    2.8194

    2.8194

    4.2083

    0.125

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    0.125

    5.5972

    1.4722

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    2.8194

    2.8194

    4.2083

    4.2083

    4.2083

    2.8194

    4.2083

    1.4722

    1.4722

    0.125

    4.25

    2.8611

    4.1667

    5.5556

    2.8611

    0.125

    4.2083

    1.4722

    1.4722

    5.5972

    2.8194

    5.5556

    4.2083

    2.8611

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    1.4722

    5.5972

    0.125

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    6.9861

    2.8611

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    8.3333

    4.1667

    2.8194

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    5.5556

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    0.125

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    4.25

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    4.2083

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    5.5556

    6.9861

    2.8194

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    6.9861

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    4.1667

    5.5972

    4.25

    5.5972

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    9.7639

    5.5972

    13.931

    5.5556

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    4.25

    1.4722

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    4.1667

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    1.4722