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In-Situ Measurements Of The Liquid-Phase Sintering Of Zinc Oxide, Mohammad Lutful Arefin

Publications and Scholarship

Polycrystalline ceramic semiconductor devices based on ZnO and several additive oxides show highly non-ohmic current-voltage behavior similar to the Zener diodes. The devices act as an insulator up to a certain electrical field called the breakdown field (EBR) but change into a highly conducting one just above it. Below and above the breakdown field they behave perfectly ohmic. This overall non-linear current-voltage characteristic together with the ability to withstand repeated high power pulses has made metal oxide varistors popular as "surge-arrestors" in electrical circuitry.

ZnO doped with Bi2O3 and Sb2O3 (ZBS), is the basic system for ceramic varistors. Phase formation …

Concentration Dependent Fluorescence Lifetime In Nanocrystalline Y2o3:Eu Phosphors, Harald Kaps, Mohammad Lutful Arefin, Ulrich Herr, Heiko Paul

Publications and Scholarship

Nanocrystalline (Y_1-xEu_x)₂O₃ powder was synthesized via a chemical vapour reaction. X-ray diffraction revealed the structure of cubic yttria with crystallite sizes of about 5 nm. The Eu-dopand concentrations x for the samples in the range from 0.003 up to 0.165 were determined by EDX-spectra. The luminescence of the nanopowders was investigated by continuous and time-resolved UV-fluorescence spectroscopy and compared to a microcrystalline Y₂O₃:Eu phosphor as a reference. The emission spectra show an increasing intensity for higher doping concentrations. However, compared to the microcrystalline material the yield was significantly lower. …