Effect of erbium doping on phase composition,mechanical and thermal properties of ZrO2-based ceramics

Er_xTi_0.1Zr_0.9–xO_2–1.5x (x = 0.04, 0.05, 0.06, 0.07, 0.08) ceramics were synthesized by a solid-state reaction method. The influence of the Er³⁺ addition on the phase composition, Vickers hardness, fracture toughness, and thermal conductivity of this ceramic material was investigated. The X-ray diffraction results reveal that the c-ZrO₂ content increases from 1.85 vol% to 33.89 vol%, and the percentage of t-ZrO₂ decreases from 98.15 vol% to 66.11 vol% with the increase in Er³⁺ content from 4 mol% to 8 mol%. Moreover, the addition of Er³⁺ is beneficial to the volume expansion of the unit cell. At the same time, the incorporation of Er³⁺ weakens the coordination of oxygen ions around the metal cations, resulting in a corresponding decrease in the tetragonality of the t-ZrO₂. The Vickers hardness and fracture toughness of the Er_xTi_0.1Zr_0.9–xO_2–1.5x ceramics show increasing and decreasing trends, respectively. The thermal conductivity has a significant decline due to point defects caused by the Er³⁺ doping. The 8ETZ ceramic exhibits the highest Vickers hardness (12.7 GPa), the lowest fracture toughness (7.6 MPa?m^1/2), and the lowest average thermal conductivity (1.85 W/(m·K)) in the temperature range of 200–1000 °C. All of the above properties are higher than those of the Y₂O₃-stabilized ZrO₂ ceramic.