Bioceramics Based on β-Calcium Pyrophosphate.

Ceramic samples based on β-calcium pyrophosphate β-CaPO were prepared from powders of γ-calcium pyrophosphate γ-CaPO with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(CHO)⋅5HO and monocalcium phosphate monohydrate Ca(HPO)⋅HO were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate CaPO). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-CaPO according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(HPO)·HO (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-CaPO) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t = 984 °C), formed from monocalcium phosphate monohydrate Ca(HPO)⋅HO, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-CaPO were biocompatible and could maintain bone cells proliferation.