Synthesis and characterization of new oxyboroapatite. Investigation of the ternary system CaO–P2O5–B2O3

The CaO–P2O5–B2O3 phase diagram was investigated at 1200 °C in order to determine the existence domain of pure apatitic oxyborophosphates with the general formula Cax(PO4)yBzOt. The prepared compounds were chemically analyzed and then characterized by X-ray diffraction, infrared absorption and Raman scattering spectroscopies. 11B and 31P magic angle spinning (MAS) NMR experiments suggest that boron is introduced as 2-fold coordinated boron BO2− in the channels of the apatitic structure and as triangular BO33− groups in the channels and substituting for PO4 groups. The present data show that a continuous solid solution is obtained inside the apatitic defined domain.