Modelling IR-spectra of single-phase polycrystalline materials with random orientation – Supplementations and refinements for optically uniaxial crystallites

• Published in: Optik (Stuttgart) Vol. 114; no. 8; pp. 351 - 359
• Main Authors: Mayerhöfer, Thomas G., Shen, Zhijian, Keding, Ralf, Höche, Thomas
• Format: Journal Article
• Language: English
• Published: Jena Elsevier GmbH 2003; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; cross-polarization; Exact sciences and technology; Infrared; Infrared and raman spectra and scattering; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; orientational averaging; Other nonmetallic inorganics; Physics; polycrystalline; orientational averaging; Infrared; cross-polarization; polycrystalline; Plasma; Powders; Uniaxial crystals; Cross polarization; Theoretical study; Infrared spectra; Reflectivity; Titanium silicates; Crystallites; Optical properties; Barium silicates; T matrix; Quaternary compounds
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1078/0030-4026-00275

The IR-reflectance spectra of a bulk sample of randomly oriented polycrystalline fresnoite (Ba 2TiSi 2O 8) are presented. The sample was prepared by Spark Plasma Sintering from a powder consisting of optically large crystallites. The spectra are of notable higher quality than those of conventionally prepared samples, especially those of the cross-polarization terms. The spectra were modelled by a 4 ×4-matrix-formalism [T. G. Mayerhöfer, J. Opt. A: Pure Appl. Opt. 4, 540 (2002)], which was refined for optically uniaxial crystals, resulting in a correct prediction of the relative peak-intensities of the cross-polarization terms. The modelling was carried out with two different orientational averaging schemes. The comparison between modelled and measured spectra revealed that the use of any weighing factor is unjustified in case of orientational averaging of the IR-optical properties of solids.