Mechanical Behaviour of Zirconia-Toughened Alumina Laminates with or without Y-PSZ Intermediate Layers

Zirconia-toughened alumina (ZTA) laminates with 5 vol% (95A) and 30 vol% (70A) of yttria-partially stabilized zirconia (Y-PSZ), as well as laminated composites with thick ZTA layers and thin Y-PSZ layers were developed and processed by means of tape casting followed by co-firing. The addition of 5 vol% Y-PSZ led to grain refinement, higher densification and an increase in mechanical properties compared to those of pure alumina. In contrast, the addition of 30 vol% Y-PSZ refined the alumina grains and formed clusters of zirconia. However, it promoted lower densification when compared to pure alumina and 95A. Nevertheless, mechanical strength increased in the 70A composites owing to the zirconia toughening mechanism. Laminated composites with intermediate Y-PSZ layers have shown thermal residual stresses after sintering as a result of the different coefficients of thermal expansion (CTE) of the components and higher performance in mechanical behaviour owing to compressive stresses in ZTA layers and to the zirconia toughening mechanism present in Y-PSZ thin layers and in ZTA with 30 vol% thick layers.