Structural, Mechanical, and Transport Properties of Scandia and Yttria Partially Stabilized Zirconia Crystals

Abstract

Crystals of (ZrO₂)_{1 –x – y}(Sc₂O₃)_x(Y₂O₃)_y (x = 0.003–0.045, y = 0.005–0.03) solid solutions have been grown by directional solidification in a cold crucible. All of the crystals consist of a mixture of two tetragonal phases of zirconia, t and t', differing in the degree of tetragonality (c/\(\sqrt 2 a\)): 1.014–1.015 and 1.004–1.005 for the t- and t'-phases, respectively. All of the crystals have high microhardness (13.5–15.0 GPa) and high fracture toughness (on the order of 6–7 MPa m^1/2). Their fracture toughness decreases with an increase in the total content of the stabilizing oxides, which is well consistent with the associated changes in phase composition, namely, with the increase in the percentage of the (transformable) t-phase. All of the crystals are similar in electrical conductivity: on the order of 0.04 S/cm at a temperature of 1173 K.