SOLID-STATE NMR INVESTIGATIONS OF DICALCIUM PHOSPHATES

Important new information about the crystal structure of dicalcium pho sphate (DCP) powders was obtained using the P-31 NMR technique. There were two types of powders under investigation. One type includes pure DA (CaHPO4) and DH (CaHPO4 . 2H(2)O) powders, and their mixtures in di fferent proportions. The other includes powders from an industrial pro duction. They were obtained by DH heating. An effective and fast metho d of identification of the structure of the nuclear nearest surroundin gs is presented, Determination of the concentration of nearest surroun dings corresponding to DA or DH types for the P-31 nuclei was demonstr ated on examples taken from production powders. Good agreement was fou nd in comparison with data obtained by chemical analysis, Especially i nteresting information is obtained by using the CP MAS NMR technique. This method allows the following conclusions about the production samp le structure to be drawn: it is a powder consisting of DH-type microcr ystals, but with numerous vacancies at the positions of water molecule s which disappeared during heating.