SYNTHESIS, X-RAY-DIFFRACTION AND SOLID-STATE P-31 MAGIC-ANGLE-SPINNING NMR-STUDY OF ALPHA-TRICALCIUM ORTHOPHOSPHATE

The effects of synthesis conditions on the quantitative preparation of alpha-tricalcium phosphate (alpha-TCP) have been investigated. The fo llowing parameters of the synthesis were considered: nature of the sta rting material - Ca-deficient hydroxyapatite, DAP, versus hydroxyapati te-anhydrous dicalcium phosphate mixtures (HAP-DCPA); Ca/P atomic rati o of the mixture, calcination temperature and time, and cooling rate. The yield and crystallinity of the final product have been estimated u sing X-ray diffraction (XRD) and solid state P-31 magic angle spinning NMR (MAS-NMR) techniques. The results show that pure, well-crystalliz ed alpha-TCP powders exhibiting nearly ideal MAS-NMR spectra, can be o btained by reactive sintering of HAP-DCPA (Ca/P = 1.50...1.52) mixture s, at 1400 degrees C for 8 h. The broadening of MAS-NMR spectra can be used as an indicator of structural order in the final product. The al pha-TCP yield with DAP was always less than 50%.