Influence of La2O3Additions on the Microstructure and Strength of Zirconia Toughened Alumina

Abstract

Despite the impressive recent developments in understanding transformation toughening, tailoring the strength of zirconia toughened alumina (ZTA) ceramics remains a major challenge. To address this chall enge, a simple powder mixing route involving ZTA powders with varying La2O3additions (0 - 10 wt.%) is investigated. In this study, flexure strength measurements were determined in accordance to the ASTM B528 standard, using three point bending method on a universal testing machine (Instron, of capacity 5 kN). The measurements were carried out under a crosshead speed of 1.0 mm/min and a pre-defined support distance of 20 mm, with at least 5 specimens being used for each data point. The highest flexure strength of ZTA ceramics recorded at 75.49 MPa for 3 wt.% of La2O3additions before decreasing to 42.95 MPa with further additions. Based on XRD analysis, a LaAl11O18phase was detected with the addition of =1 wt. % of La2O3which proved that the solubility limit was exceeded compositionally. Meanwhile, microstructural investigation of these ZTA-La2O3ceramics revealed formations of elongated LaAl11O18grains, clearly present between the La2O3and ZrO2grains. This work provides newfound evidences for the possibility of strength-tailored ZTA ceramics, which is key for the design and fabrication of economical high-performance ceramics in years to come.