Ceramics Based on Sodium Rhenanite CaNaPO4, Obtained via Firing of Composite Cement-Salt Stone

Ceramics based on rhenanite CaNaPO4 with density of 0.94 g/cm3 and compressive strength of 10.3 MPa was obtained via firing at 900 °C of composite cement-salt stone prepared from a hardening powder mixture of calcium citrate tetrahydrate Ca3(C6H5O7)2∙4H2O and sodium dihydrogen phosphate NaH2PO4. The phase composition of the obtained samples of cement–salt stone was represented by monetite CaHPO4, unreacted sodium dihydrogen phosphate and calcium citrate tetrahydrate. According to the XRD data, the phase composition of the ceramic samples after annealing in the temperature range of 500–700 °C was mainly represented by the β-CaNaPO4 phase. It was found that after an annealing at temperature of 900 °C, the phase composition of ceramics was presented with the only phase of β-CaNaPO4. It was demonstrated that an increase in the annealing temperature led to an increase in the grain size from 1 μm after annealing at 500 °C to 5 μm after annealing at 900 °C. Obtained ceramic material based on CaNaPO4 could be important for regenerative treatments of bone tissue defects.