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Ceramic materials in Na2O-CaO-P2O5 system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca3(C6H5O7)2∙4H2O, monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2∙H2O and/or sodium dihydrogen phosphate NaH2PO4. The phase composition of the obtained samples of cement-salt stone after adding water, hardening and drying included brushite CaHPO4∙2H2O, monetite CaHPO4 and also unreacted Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and/or NaH2PO4. The phase composition of ceramics in Na2O-CaO-P2O5 system obtained by firing cement-salt stone was formed due to thermal conversion of hydrated salt and heterophase reactions between components presented in samples during firing. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O and Ca(H2PO4)2∙H2O after firing at 900 °C included β-calcium pyrophosphate (CPP) β-Ca2P2O7. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, and NaH2PO4 after firing at 900 °C included β-sodium rhenanite β-CaNaPO4. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and NaH2PO4 after firing at 900 °C included β-Ca2P2O7, β-CaNaPO4, double calcium-sodium pyrophosphate Na2CaP2O7, and Na-substituted tricalcium phosphate Сa10Na(PO4)7. Obtained ceramic materials in Na2O-CaO-P2O5 system including biocompatible and biodegradable phases could be important for treatments of bone tissue defects by means of approaches of regenerative medicine.

Biocompatibility of ceramic materials in Ca2P2O7-Ca(PO3)2 system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca2P2O7-Ca(PO3)2 system were obtained by annealing cement-salt stone based on powder mixtures of calcium citrate tet-rahydrate Ca3(C6H5O7)2·4H2O and monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2·H2O. The phase composition of cement-salt stone included brushite, monetite as a result of chemical reaction of starting components after adding of water. The presence of citric acid as by-product of chemical reaction, leads to increase the setting time of the cement-salt stone. Highly concentrated aqueous suspensions based on calcium citrate and MCPM powders providing content of calcium polyphosphate Ca(PO3)2 up to 20 wt % in ceramics were used for designing bioresorbable materials. The presence of an excess of monocalcium phosphate monohydrate makes it possible to reduce the annealing temperature of ceramics, which is associated with the formation of a lower melting phase of Ca(PO3)2. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects.

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.