Mechanical and Dielectric Loss Measurements in Y2O3-ZrO2 and TiO2-Y2O3-ZrO2 Ceramics

Tetragonal zirconia with varying contents of Y₂O₃ (2-4 mol %) and (additional) TiO₂ (0 - 15 mol %) were prepared by coprecipitation. Mechanical loss (internal friction) measurements show a distinct loss maximum at about 380 K (1 Hz); it correlates with a dielectric loss maximum at about the same temperature. The loss maximum is attributed to thermally activated (localized) reorientation of pairs of oxygen vacancies and yttrium ions constituting elastic and electric dipoles. For higher Y₂O₃ contents (≲4 mol %) a satellite maximum appears at ≃ 500K (1 Hz); its height increases by post sinter annealing (8 to 36h at ≈ 1700K). The 500 K maximum is assigned to larger agglomerates of yttrium ions with oxygen vacancies. Comparative mechanical and electrical impedance measurements on 3Y-TZP (by variation of frequency) indicate that the localized reorientation of the dipoles contributes to the “bulk semicircle.”