STUDY OF PARTIALLY STABILIZED CE DOPED ZRO2 CRYSTALS BY ELECTRON PARAMAGNETIC RESONANCE

The study of crystals of ZrO2 solid solutions (PSZ) stabilized with yttrium and cerium oxides was carried out by electron paramagnetic resonance (EPR) in the X and Q range. The presence of Zr3+ centers in annealed ZrO2 crystals stabilized only by yttrium oxide (2.8 mol.% Y2O3) is established. Another kind of paramagnetic O−centers appear when CeO2 is added to ZrO2 crystals in addition to yttrium oxide. To estimate the concentration of Ce3+ ions in PZS crystals, EPR spectra were recorded in the presence of a reference specimen at 7 K. Paramagnetic Ce3+ ions have been identified and their relative amounts in PSZ crystals before and after high−temperature heat treatment has been measured. The annealing in air leads to a decrease in the concentration of Ce3+ ions for all compositions and changes the color of the crystals from red to white. After annealing in the 2.0Y0.8Ce3Zr sample, the amount of paramagnetic Ce3+ ions decreased approximately twice. Paramagnetic centers from Ce3+ are not detected in a the sample with a low cerium content of 0.1 mol.% after annealing which indicates the complete transition of Ce3+ to the Ce4+ state. It is shown that the formed paramagnetic centers of cerium are bound by strong exchange interactions. No angular dependence of the EPR lines for the paramagnetic Ce3+ cations on the applied external magnetic field was observed. The probable reason for the absence of such angular dependence is that impurity rare−earth ions are located next to each other, forming impurity clusters with effective spin Seff = 1/2.

EPR, partially stabilized zirconia dioxide

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