The influence of Sr and Mn incorporated ions on the properties of microwave single- and two-step sintered biphasic HAP/TCP bioceramics

Abstract

The aims of this study were to investigate the effects of Sr- and Mn-doped ions on the sintering behaviors, microstructure and mechanical properties of the bioceramics processed by single- and two-step microwave sintering (MWSSS and MWTSS). Nano-sized calcium hydroxyapatite powders doped with Sr and Mn ions, obtained by modified precipitation synthesis, were isostatically pressed at 400 MPa and processed by MWSSS and MWTSS at different temperatures. In all cases during the sintering, the doped HAP powders turned into biphasic mixtures of HAP and TCP, but the amount of TCP was certainly lower in the case of MWTSS. It was shown that the doped ions significantly affected: density, microstructure, grain size, porosity, hardness, and fracture toughness of the processed bioceramics. Two-step microwave sintering was successfully applied for the processing of HAP/TCP bioceramics doped with strontium and manganese ions. Both two-step microwave sintered doped bioceramics had similar and high hardness values, but the strontium-substituted bioceramic material certainly had higher fracture toughness (1.54 MPam(1/2)), with an average grain size of 195 nm. Based on the results presented in this paper, it was concluded that the two-step microwave sintered strontium-doped bioceramics could be suitable materials in the bone regenerative field.