Influence of gadolinia on thermal expansion property of ZrO₂-4.5 mol%Y₂O₃ ceramics

This paper concentrates on the influence of gadolinia on structure and thermal expansion property of ZrO₂-4.5 mol%Y₂O₃ (YSZ) ceramics. The YSZ-xGd₂O₃ (0 ≤ x ≤ 7.5 in mol%) ceramics were synthesized by solid state reaction method at 1500 °C for 2 h in air. The relative density, phase structure and thermal expansion property of YSZ-xGd₂O₃ ceramics were investigated by the Archimedes method, X-ray diffraction and high-temperature dilatometer. The thermal expansion coefficients of YSZ-xGd₂O₃ ceramics increase with the increase in temperature. The thermal expansion coefficients of YSZ-xGd₂O₃ ceramics first decrease with increasing the mole fraction (x) of gadolinia from x = 0 (YSZ) to x = 4.5 (YSZ-4.5Gd₂O₃), and then increase from x = 4.5 (YSZ-4.5Gd₂O₃) to x = 7.5 (YSZ-7.5Gd₂O₃) in the temperature range of 50-1200 °C. The YSZ-4.5Gd₂O₃ ceramics have the lowest thermal expansion coefficient in YSZ-xGd₂O₃ ceramics, which is due to formation of the (G d^′_Zr V_Ö Y^′_Zr) ionic vacancy clustering.