Effect of heat treatment on the thermal conductivity of single crystals of ZrO$_{2}$-based solid solutions stabilized with scandium and yttrium oxides

The effect of heat treatment at 1000$^{\circ}$C for 400 h on the thermal conductivity of zirconium dioxide crystals stabilized with scandium oxide (ZrO$_2$)$_{1-x}$(Sc$_{2}$O$_3)_{x}$ ($x$ = 0.08–0.10) and simultaneously with scandium and yttrium oxides (ZrO$_2)_{1-x-y}$(Sc$_{2}$O$_3)_{x}$(Y$_{2}$O$_3)_{y}$ ($x$ = 0.003–0.20; $y$ = 0.02–0.025). has been studied. In the crystals of zirconium dioxide stabilized with scandium oxide, the most noticeable changes in the thermal conductivity are observed in the 9ScSZ crystals, in which the phase composition is changed and a marked content of the rhombohedral phase appears. These changes are less noticeable in the 8ScSZ crystals and they are mainly due to the ordering of oxygen vacancies and the changes in the microstructures of the samples, and there are no changes in the 10ScSZ crystals. The 10ScSZ crystals have the minimum electrical conductivity before and also after annealing, which is determined by the highest content of scandium oxide in the solid solution. Insignificant changes in the thermal conductivity are observed in crystals of partially stabilized zirconium dioxide co-alloyed with scandium and yttrium oxides. The cubic 8Sc2YSZ and 10Sc2YSZ crystals demonstrate only slight changes in the thermal conductivity, the character of the temperature dependence of the thermal conductivity, and the phase compositions. The alloying of the zirconia–based solid solutions with yttrium oxide simultaneously with scandium oxide enables one to increase the stability of their phase compositions and structurally dependent thermal and electrical physical characteristics.