Hydrothermal synthesis of single-crystal α-tristrontium phosphate particles

Anisotropic ceramic bodies can be fabricated by a reactive template grain growth method; however, template particles with suitable powder properties are required to create the ceramics with well controlled anisotropy. Therefore, we synthesized well-isolated α-tristrontium phosphate (α-TSP) particles with a hexagonal plate-like shape as template particles for anisotropic strontium apatite ceramics using α-strontium hydrogen phosphate (α-SrHPO4) precursor particles. Three synthetic parameters were varied: (i) precursor particle size, (ii) stirring rate, and (iii) hydrothermal temperature. Well-isolated hexagonal plate-like α-TSP single-crystal particles were successfully synthesized by hydrothermal treatment at 150 °C for 3 h at a stirring rate of 150 rpm using fine α-SrHPO4 precursor particles. The developed plane of the hexagonal plate-like α-TSP particles was determined to be the {00l} plane, and the side planes were revealed to be not {h00} planes, but inclined {h0l} planes. The resulting α-TSP particles may provide a promising template for the development of anisotropic apatite-based ceramics.