Ceramics-Silikáty 43, (4) 157 - 164 (1999)

Three different crystallographic modifications of mineral brianite were prepared from the melt. The temperatures of modification changes determined by DTA were 760 and 900 °C, respectively. The interaction of all modifications with simulated body fluid (SBF) and with distilled water was studied. Hydroxyapatite was identified on the sample surfaces after the interaction of brianite with SBF using X-ray diffraction and X-ray microanalysis suggesting possible bioactivity. The time dependence of amount of brianite components i in the solution can be described using equation NL_i=B_i/K_i [1-exp(-K_it)]+W_it. Considering general composition of precipitated layer Ca_xMg_(10-x)(PO₄)₆(OH)₂, the rate of dissolution and the rate of precipitation were estimated from W_i parameters using iteration method. Stoichiometric parameter x changes in interval 5.2-9.7. The dissolution and precipitation rates depend on crystallographic modification both in SBF and in distilled water. Higher values of both precipitation and dissolution rates were found for the interaction of γ modification in all solutions studied compared to α and β modifications.