Optical Properties and Thermal Effects in CaSZ and YSZ Single Crystal by Raman Scattering, Photoluminescence and Absorption Spectroscopy

Abstract

AbstractTemperature dependent Photoluminescence (PL) and Raman spectra have been used to study the defect structure of untreated and thermochemically reduced calcia stabilized zirconia (CaSZ) and yttria stabilized zirconia (YSZ) single crystals. Over the whole temperature range studied the emission (EM) spectrum of the untreated crystals can be decompose into three broad bands, indicating the presence of several radiative electron transitions which can be associated with anion vacancies centers. Results points out to intrinsic F type centers and extrinsic F type centers (FA, FAA) as the main defect generated in the stabilization process. Effect of thermal reduction on the Raman activity caused a decreased in the acoustic mode region and a shift in the maximum of the excitation (EX) spectra. These variations can be related to a broad absorption band centered at ∼365 nm. This is consistent with a nonrandom arrangement of vacancies, which produces the superposition of periodic sequences of vacancies within domains. Concentration of the color centers was determined by optical absorption in the UV-VIS region. PL temperature dependence study in colored samples suggest that no significant new defect was generated in the reduction process, but a recombination of the charges states of the initial intrinsic and extrinsic F centers.