Line-broadening effects in the powder infrared spectrum of apatite

Balan, Etienne and Delattre, Simon and Roche, Damien and Segalen, Loïc and Morin, Guillaume and Guillaumet, Maxime and Blanchard, Marc and Lazzeri, Michele and Brouder, Christian and Salje, Ekhard K. H. (2010) Line-broadening effects in the powder infrared spectrum of apatite. Physics and Chemistry of Minerals, 38 (2). pp. 111-122. DOI 10.1007/s00269-010-0388-x

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Abstract

The crystallinity of natural and synthetic apatite samples is often determined from the broadening of ν 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 ν 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.

Item Type: Article
Uncontrolled Keywords: 2010AREP (add); IA59
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physics and Chemistry of Minerals
Volume: 38
Page Range: pp. 111-122
Identification Number: 10.1007/s00269-010-0388-x
Depositing User: Sarah Humbert
Date Deposited: 08 Feb 2012 12:34
Last Modified: 23 Jul 2013 10:03
URI: http://eprints.esc.cam.ac.uk/id/eprint/2377

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