Thermal expansion of mullite-type Bi2Al4O9: A study by X-ray diffraction, vibrational spectroscopy and density functional theory

MURSHED M.M.; MENDIVE C.; CURTI M.; SEHOVIC M.; FRIEDRICH A.; FISCHER M.; GESING TH. M.

JOURNAL OF SOLID STATE CHEMISTRY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2015 vol. 229 p. 87 - 96

0022-4596

The lattice thermalexpansion of mullite-type Bi2Al4O9 was studiedusing X-ray diffraction, Raman spectroscopy and density functional theory(DFT). The metric parameters were modeled using Grüneisen second-orderapproximation for the zero pressure equation of state, where the temperature-dependentvibrational internal energy was calculated from Debye characteristic frequency.Whereas the first-order Grüneisen approximation (vibrational energy wascalculated from Debye-Einstein-Anharmonicity approach) resulted almostidentical Debye temperature for volumetric expansion, the second-order approachwas used to calculate physically meaningful axial parameters. The phonondensity of states as well as phonon dispersion helped guide to set the characteristicfrequency for simulation. The experimental infrared and Raman phonon bands werecompared with those calculate from the DFT. Selective optical phonon bands wereanalyzed for the thermal anharmonic behaviors using simplified Klemens model.The respective mode Grüneisen parameters were calculated from thepressure-dependent Raman spectra.