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The effect of yttria on the solid reaction mechanism of a CaHPO4·2H2O + CaCO3 system at different temperatures was experimentally stud-ied. The samples with and without yttria were subjected to thermogravimetric/differential scanning calorimetry measurement. The samples were heat treated at the temperatures corresponding to the peaks on the DSC spectra, and the resulted phase compositions were identified by X-ray diffraction. The transformation mechanism was deduced by comparing the phases obtained at different temperatures. The results show that the transformations at below 1073 K are not affected by yttria, but all those at above 1073 K are completely altered. The formation tem-perature of hydroxyapatite decreases by 134 K, and the decomposition temperature increases by 38 K. The polymorphous transformation of Ca3(PO4)2 from β phase to α phase increases by 47 K. The thermodynamic properties of the transformations at above 1073 K are also modi-fied by the addition of yttria; that is, the endothermal peaks are substituted by exothermal peaks.
The effect of yttria on the solid reaction mechanism of a CaHPO4 · 2H2O + CaCO3 system at different temperatures was experimentally stud-ied. The samples with and without yttria were subjected to thermogravimetric / differential scanning calorimetry measurement. The samples were heat treated at the temperatures The transformed mechanism was derived by comparing the phases obtained at different temperatures. The results show that the transformations at below 1073 K are not affected by The formation of tem-perature of hydroxyapatite decreases by 134 K, and the decomposition temperature increases by 38 K. The polymorphous transformation of Ca3 (PO4) 2 from β phase to α phase increases by 47 K. The thermodynamic properties of the transformations at above 1073 K are also modi-fied by the addition of yttria; that i s, the endothermal peaks are substituted by exothermal peaks.