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

• Published in: Journal of solid state chemistry Vol. 229; pp. 87 - 96
• Main Authors: Mangir Murshed, M., Mendive, Cecilia B., Curti, Mariano, Šehović, Malik, Friedrich, Alexandra, Fischer, Michael, Gesing, Thorsten M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2015
• Subjects: Density functional theory; Equation of state; Modeling; Mullite-type; Phonon; Thermal expansion; Thermal expansion; Density functional theory; Mullite-type; Modeling; Equation of state; Phonon
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2015.05.010

Polycrystalline Bi2Al4O9 powder samples were synthesized using the glycerine method. Single crystals were produced from the powder product in a Bi2O3 melt. The lattice thermal expansion of the mullite-type compound was studied using X-ray diffraction, Raman spectroscopy and density functional theory (DFT). The metric parameters were modeled using Grüneisen approximation for the zero pressure equation of state, where the temperature-dependent vibrational internal energy was calculated from the Debye characteristic frequency. Both the first-order and second-order Grüneisen approximations were applied for modeling the volumetric expansion, and the second-order approach provided physically meaningful axial parameters. The phonon density of states as well as phonon dispersion guided to set the characteristic frequency for simulation. The experimental infrared and Raman phonon bands were compared with those calculate from the DFT calculations. Selective Raman modes were analyzed for the thermal anharmonic behaviors using simplified Klemens model. The respective mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. Crystal structure of mullite-type Bi2Al4O9 showing the edge-sharing AlO6 octahedra running parallel to the c-axis. [Display omitted] •Thermal expansion of Bi2Al4O9 was studied using XRD, FTIR, Raman and DFT.•Metric parameters were modeled using Grüneisen approximation.•Phonon DOS and phonon dispersion helped to set the Debye frequency.•Mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra.•Anharmonicity was analyzed for some selective Raman modes.