Linear thermal expansion coefficient of Al2O3/LaPO4 ceramic composite

Machining is inevitable for flexible use of advance ceramic materials such as alumina. A lot of research has been focused on improvement of ceramic machinability. Generally, the addition of layered materials such as LaPO4 to ceramic matrix (Al2O3) was used to improve the machinability, as LaPO4 was stable and compatible with Al2O3 upto 2023 K in air .The LaPO4-Al2O3 interface was found to be sufficiently weak. The layered structure of LaPO4 and the weak interface at Al2O3/LaPO4 grain boundaries are the main reason for the improvement of the machinability. In Al2O3/LaPO4 composite highly machinable structure (LaPO4) is located at the material surface, and the high performance structure (Al2O3) providing excellent mechanical properties is located inside. The Al2O3/LaPO4 composites are easily machined using cemented carbide tools instead of conventional diamond tools. The improved machinability of Al2O3/LaPO4 composites is very essential and important for broad engineering applications and the material must have dimensional integrity and must not develop micro-cracks when operational in thermal environment. There are few systematic studies on the (1-x)Al2O3-xLaPO4 (x = 0 to 100 wt % ) composite ceramics, including fabrication methods and their material properties. The thermal expansion coefficient is one of the important thermo-physical properties of materials for design of new materials especially for use at high temperature. In this paper linear thermal expansion coefficient of (1-x)Al2O3-xLaPO4 (x = 30 and 50 wt% ) was measured using dilatometer, supplied by NETZSCH, Germany