Balan Etienne auteur aut IRD Delattre S. auteur aut IRD Roche D. auteur aut IRD Segalen L. auteur aut IRD Morin G. auteur aut IRD Guillaumet M. auteur aut IRD Blanchard M. auteur aut IRD Lazzeri M. auteur aut IRD Brouder C. auteur aut IRD Salje E. K. H. auteur aut IRD text journalArticle eng text/pdf born digital access The crystallinity of natural and synthetic apatite samples is often determined from the broadening of nu (4) PO4 infrared absorption bands. However, various physical mechanisms contribute to the observed linewidth. In the present study, the factors determining the linewidth in the powder spectrum of synthetic fluorapatite and hydroxyapatite samples are investigated. The temperature dependence of the infrared spectrum (10-270 K) is used to assess the respective contributions of homogeneous broadening, related to the decay of phonons through anharmonic coupling, and heterogeneous broadening related to elastic strain and macroscopic electrostatic effects. This latter contribution is dominant in the investigated samples and depends on the shape of powder particles. It is discussed under the light of the theoretical modeling of the low-frequency dielectric properties of apatite based on first-principles density functional theory calculations. The linewidth of the weak nu (1) PO4 absorption band provides a reliable information on microscopic sources of broadening, i.e., apatite crystallinity. In comparison, the other more intense PO4 bands are more sensitive to long-range electrostatic effects. specialized Apatite Infrared spectroscopy First-principles calculations Anharmonicity 064 38 2 111-122 2011 0342-1791 https://www.documentation.ird.fr/hor/fdi:010053164 10.1007/s00269-010-0388-x 0342-1791 [F B010053164] https://www.documentation.ird.fr/hor/fdi:010053164 https://www.documentation.ird.fr/intranet/publi/2011/03/010053164.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2011-04-07 2017-08-23 fdi:010053164 fre