Abstract

The synthesis of double phosphates based on calcium and alkali metals from different two-phase mixtures was studied. The phase relationships in the CaO–K₂O–P₂O₅ and CaO–Na₂O–P₂O₅ system were clarified, especially the phase transition temperature in potassium rhenanite CaKPO₄. It was shown that some compounds that are mentioned in the literature, in particular, CaK₂P₂O₇, CaNa₂P₂O₇, CaK₄(PO₄)₂, and CaNa₄(PO₄)₂, cannot be obtained at 1000–1200°C at normal pressure. The densification and recrystallization were investigated during the reaction sintering of selected two-phase mixtures. Reaction sintering of a mixture of Ca₃(PO₄)₂ and CaK₄(PO₄)₂ gives CaKРO₄ ceramic with a density of 78% (linear shrinkage of the sample is 5%); when sintering a mixture of K₂CO₃ and Ca₂P₂O₇, the density of ceramic was 62% with a linear shrinkage of 15%. The reaction sintering of sodium-containing mixtures made it possible to obtain dense ceramics (density above 90%, linear shrinkage more than 6.5%) from a mixture of CaNa₄(PO₄)₂ and Ca₃(PO₄)₂. The experimental features of the reaction sintering of calcium and potassium/sodium double phosphates are discussed from the point of view of volume change during the course of the reaction. Another aspect that determines the density and microstructure of ceramics is the phase transformation of α → β in alkali metal rhenanites CаMPO₄.

中文翻译：

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基于磷酸钙CaMPO 4（M = K，Na）的生物陶瓷的反应烧结

摘要

研究了从不同的两相混合物中合成基于钙和碱金属的双磷酸盐。阐明了CaO–K ₂ O–P ₂ O ₅和CaO–Na ₂ O–P ₂ O ₅体系中的相关系，尤其是钾锰矿CaKPO _4中的相变温度。已显示文献中提到的一些化合物，特别是CaK ₂ P ₂ O ₇，CaNa ₂ P ₂ O ₇，CaK ₄（PO ₄）₂和CaNa ₄（PO ₄）₂，在常压下于1000–1200°C下无法获得。在选择的两相混合物的反应烧结过程中研究了致密化和重结晶。反应的Ca的混合物的烧结₃（PO ₄）₂和CAK ₄（PO ₄）₂给出CaKРO ₄陶瓷具有78％的密度（样品的线性收缩为5％）; 烧结K ₂ CO ₃和Ca ₂ P ₂ O ₇的混合物时，陶瓷密度为62％，线性收缩率为15％。含钠混合物的反应烧结使得可以从CaNa ₄（PO ₄）₂和Ca ₃（PO ₄）₂的混合物中获得致密陶瓷（密度大于90％，线性收缩率大于6.5％）。从反应过程中的体积变化的角度讨论了钙和钾/钠双磷酸盐的反应烧结的实验特征。确定所述密度和陶瓷的微结构的另一个方面是α→β在碱金属相变rhenanitesCаMPO ₄。