Partially stabilized Y2O3–ZrO2 (Y-PSZ) is often used as a material in the field of oxygen sensors and batteries. However, the presence of a tetragonal phase will seriously reduce the conductivity of Y-PSZ materials. As a sintering aid, Bi2O3 can be used to sinter materials with high oxygen ion conductivity at low temperatures. It is the first choice for the Y-PSZ doped system. A new microwave sintering technique prepared Bi2O3–Y-PSZ powders. The effects of doping amount of Bi2O3 on the microstructure, phase transition, and tetragonal phase content of Y-PSZ during sintering were researched. The results displayed that doping Bi2O3 improved the tetragonal phase content of the ZrO2. The tetragonal phase content of the samples increased from 59.72% to 94.69% after sintering at 750 °C for 1 h. After doping Bi2O3, the aggregation of the samples reduced gradually, and the particles dispersed evenly. The average particle sizes of raw material and samples doped with different amounts of Bi2O3 were 0.0794 μm, 0.0638 μm, 0.0629 μm, 0.0794 μm, 0.1116 μm, respectively. Therefore, in the doping amount (1 mol%-4 mol%), the Bi2O3 doped Y-PSZ system with 2 mol% has the highest tetragonal phase content, the best dispersion, the smallest average particle size, and the most uniform particle distribution.
