Electron paramagnetic resonance of titanium impurities in reduced yttria-stabilized zirconia

The electronic defects in single crystals of yttria-stabilized have been zirconia (YSZ) have been examined using electron paramagnetic resonance (EPR). The EPR spectra of hydrogen-reduced YSZ single crystals are almost identical to those of polycrystalline yttria (12 mol%)-stabilized zirconia-titania, indicating that the Ti3+ cation is the predominant electronic defect in both materials. The disparity between the discoloration of the polycrystals and single crystals (blue vs yellow) is attributed to the different crystalline environments of the Ti3+ cations in the grain boundaries and lattice. The concentration of titanium cations in the YSZ single crystals (ca. 600 ppm) is probably too dilute to contribute to the electronic conductivity