Mechanical properties and aging resistance of calcia-yttria co-stabilized zirconia: from powder to ceramic

In this study, divalent calcium cation with large radius and trivalent yttrium cation with small radius were introduced to develop co-stabilized zirconia ceramics with both superior mechanical properties and aging resistance. Through a reverse coprecipitation-hydrothermal method, a series of ultrafine x CaO- y Y 2 O 3 -ZrO 2 ( x = 2.0, 3.0, y = 0.5, 1.0, 1.5, 2.0 ) raw powders with high quality were fabricated for the production of nanostructured ceramics via low-temperature pressurelessly sintering. The sintering process was optimized by investigating the effects of sintering temperature on densification, grain growth and phase evolution. The minimally doped 2.0 CaO- 0.5 Y 2 O 3 -ZrO 2 ceramic retained pure tetragonal phase at room temperature, achieving a balance of excellent toughness and high aging resistance. The impacts of chemical composition on microstructure, hardness, toughness and aging resistance were examined for these x CaO- y Y 2 O 3 -ZrO 2 ( x = 2.0, 3.0, y = 0.5, 1.0, 1.5, 2.0 ) ceramics. The segregation of calcium and yttrium cations at grain boundaries effectively tailored the microstructure. It was observed that substituting small trivalent yttrium cations for large divalent calcium cations effectively enhanced the aging resistance without sacrificing mechanical properties, due to the strengthened grain boundaries and asymmetrical distribution of cations among grains. This work not only produces low-doped zirconia ceramics with both excellent mechanical properties and aging resistance, but also presents straightforward method for preparation of high-quality raw powders and delicate microstructural engineering during sintering for developing advanced structural ceramics.