title: Temperature dependence of single-crystal elastic constants of flux-grown alpha-GaPO(4).
abstract: The lattice parameter change with respect to temperature (T) has been measured using high-temperature powder X-ray diffraction techniques for high-temperature flux-grown GaPO(4) single crystals with the alpha-quartz structure. The lattice and the volume linear thermal expansion coefficients in the temperature range 303-1173 K were computed from the X-ray data. The percentage linear thermal expansions along the a and c axes at 1173 K are 1.5 and 0.51, respectively. The temperature dependence of the mass density rho of flux-grown GaPO(4) single crystals was evaluated using the volume thermal expansion coefficient alpha(V)(T) = 3.291 x 10(-5) - 2.786 x 10(-8) [T] + 4.598 x 10(-11)[T](2). Single-crystal high-resolution Brillouin spectroscopy measurements have been carried out at ambient pressure from 303 to 1123 K to determine the elastic constants C(IJ) of high-temperature flux-grown GaPO(4) material. The single-crystal elastic moduli were calculated using the sound velocities via the measured Brillouin frequency shifts Deltanu(B). These are, to our knowledge, the highest temperatures at which single-crystal elastic constants of alpha-GaPO(4) have been measured. Most of the room-temperature elastic constant values measured on flux-grown GaPO(4) material are higher than the ones found for hydrothermally grown GaPO(4) single crystals. The fourth-order temperature coefficients of both the Brillouin frequency shifts T(nuB)((n)) and the single-crystal elastic moduli T(C(IJ))((n)) were obtained. The first-order temperature coefficients of the C(IJ) are in excellent agreement with previous reports on low-temperature hydrothermally grown alpha-GaPO(4) single crystals, while small discrepancies in the higher-order temperature coefficients are observed. This is explained in terms of the OH content in the GaPO(4) network, which is an important parameter in the crystal thermal behavior.
authors.affiliation: Institut Charles Gerhardt Montpellier, UMR5253 CNRS-UM2-ENSCM-UM1, PMOF, UMII, CC1504, Place E. Bataillon, 34095 Montpellier Cedex 5, France. pascale.armand@.univ-montp2.fr
authors.forename: P
authors.initials: P
authors.lastname: Armand
authors.forename: M
authors.initials: M
authors.lastname: Beaurain
authors.forename: B
authors.initials: B
authors.lastname: Rufflé
authors.forename: B
authors.initials: B
authors.lastname: Menaert
authors.forename: P
authors.initials: P
authors.lastname: Papet
mesh_terms: D003460:Crystallization; D005708:Gallium / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D033362:Powder Diffraction; D013696:Temperature
chemical_list: D010710:Phosphates; D005708:Gallium