Thermodynamic modelling assisted three-stage solid state synthesis of high purity β-Ca3(PO4)2

•Thermodynamic modelling was used to predict the reaction pathways, optimal temperature, and possible impurity phases during β-TCP formation.•Three stage synthesis design was successfully developed to produce high purity (>99 %) β-TCP with consistent reproducibility.•The optimal synthesis temperature was experimentally determined to be 1000 °C in agreement with the theoretical calculations.•Separation of heating stages into 350 °C, 680 °C, and 1000 °C effectively minimized secondary phosphate phases and enhanced product purity.