Controllable preparation of 5mol% Y2O3-stabilized tetragonal ZrO2 by hydrothermal method

Abstract

As a critical solid electrolyte material, 5 mol% yttrium stabilized tetragonal zirconia (5YSTZ) is commonly synthesized by hydrothermal . In this work, in order to explore the crystallization mechanism and achieve controllable preparation, six precursors with different zirconium coordination and yttrium/zirconium mixing state were used to hydrothermally synthesize nanostructured 5YSTZ. By analyzing elemental distribution, phase structure and microstructure of obtained samples, we have found that 5YSTZ follows different crystallization mechanisms under different preparation conditions: dissolution-crystallization is the major mechanism when using negatively charged zirconium coordination as precursor, while in-situ mechanism dominates when using positively charged zirconium coordination as precursor. This means the crystallization and phase structure of 5YSTZ can be adjusted by controlling the zirconium coordination in precursor. Significantly, 5YSTZ produced by precursor with uniformly mixed yttrium and negatively charged zirconium coordination has the highest densification (>99%) and ionic conductivity (34.09 mS/cm) measured at 850 °C, with the lowest activation energy (0.93eV).