Étude Infrarouge de Phosphates de Calcium de la Famille de L'Hydroxylapatite

Abstract

This article deals with infrared spectroscopic studies, in the range 400-4OOOcm-~, of some calcium phosphates having an apatitic structure. The bands are assigned and small differences between some spectra ale explained.Occurrence of free OH-groups in the apatitic cell is confirmed; acidic phosphate groups, linked together by hydrogen bonds, have been detected in the spectra of compounds having a C a p value lower than the hydroxylapatite one.Heat effect upon the constitution of these compounds has also been studied; these infrared data get information which could not be obtained by X rays spectrography: i.e. the occurrence of pyrophosphate groups in solid solution in the apatihc cell.The experimental data are satisfactorily explained by the assumption that H+ ions are able to (<substitute)) progressively Ca++ ions in the apatitic structure.An original formula is proposed for the a tricalcium phosphate. I. POSITION DU P R O B L~Le probltme de la constitution et de la structure des orthophosphates de calcium de type apatitique a prtoccupk de nombreux chercheurs appartenant ?t diverses disciplines et utilisant des techniques varikes d 'investigation.Nous nous sommes kgalement intkressks a cette question que nous avons soumise 21 l'examen de diverses mkthodes physicochimiques et principalement ii celui de la spectromktrie infrarouge; nous nous limiterons, dans cet article, ii l'exposk des rksultats obtenus par cette mkthode.Rappelons que, lorsqu'on synthktise en milieu aqueux des orthophosphates de calcium, on obtient, suivant les quantitks de rkactifs utiliskes et, aussi, suivant leur temperature, des composCs qui, ii l'analyse chimique, accusent des rapports Ca/P diffkrents, mais donnent des