A new model for the location and distribution of carbonate ions in carbonated apatite was used to assign the IR spectra of A- and AB-carbonated apatites. The percentage of total carbonate as measured by the mass loss in the TGA of these compounds is in good agreement with the percentage obtained by combustion analysis. The decomposition of pure A-type carbonate appears at temperatures of 985–1123 °C, whereas the decomposition of AB-type carbonated apatites occurs in the range of 600–800 °C. This difference is attributed to changes in the environment of channel carbonate brought about by B-type substitution of carbonate for phosphate. In the presence of sodium ions, the channel is changed by substitution of sodium for calcium in order to accommodate the difference between the charge of the carbonate and phosphate ions. A thermodynamic cycle is introduced to rationalize the differences in decomposition temperatures of A- and B-type carbonate. Preferential loss of B-type carbonate upon heating to 600 °C also suggests the migration of B-type carbonate to A-sites.

中文翻译：

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碳化磷灰石热行为合理化的新模型

碳酸盐磷灰石中碳酸盐离子的位置和分布的新模型用于指定A和AB碳酸磷灰石的红外光谱。通过这些化合物的TGA中的质量损失测量的总碳酸盐的百分比与通过燃烧分析获得的百分比非常一致。纯A型碳酸盐的分解出现在985-1123°C的温度下，而AB型碳酸磷灰石的分解发生在600-800°C的范围内。这种差异归因于由碳酸盐的B型取代磷酸盐引起的通道碳酸盐环境的变化。在存在钠离子的情况下，通过用钠替代钙来改变通道，以适应碳酸盐和磷酸根离子之间的电荷差异。引入热力学循环以合理化A型和B型碳酸盐的分解温度差异。加热至600°C时B型碳酸盐的优先损失也表明B型碳酸盐向A位迁移。