Microstructure and Mechanical Properties of Spark Plasma Sintered Amorphous AlPO4 Ceramics

The main objective of this study is to assess the structure and mechanical properties of amorphous aluminum phosphate (AlPO4) ceramic specimens prepared through Spark Plasma Sintering (SPS) method. To this end, AlPO4 powder was synthesized through sol-gel process and consolidated by SPS at the sintering temperature range of 800-1300 °C. Ceramic specimens were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses. Bulk density of the samples was measured using Archimedes’ principle. In addition, hardness and indentation fracture toughness of the samples were determined to identify the mechanical properties. The results from XRD analysis, SEM images, and density measurement revealed that the sintered sample was characterized by an amorphous structure with the porosity of ~ 3 % and relative density of 97 % after SPS at 1000 °C for 15 min. Increasing the temperature to 1300 °C made the amorphous AlPO4 crystallized. The fracture toughness was obtained to be 5.75 MPa.m1/2 under this sintering condition. Crack deflection around porosities was identified as the main toughening mechanism involved.