Effect of Particle Size and Shape on the Infrared Absorption Spectra of Barium Titanate and Strontium Titanate Powders

Abstract

Effects of particle size and particle shape have been studied in the infrared absorption spectra of BaTiO3 and SrTiO3 powders to determine whether previously developed methods to treat such effects are applicable to crystals having high dielectric constant and ``soft'' lattice modes. The spectrum of both materials exhibits three absorption bands (BaTiO3: 545, 400, and 180 cm−1; SrTiO3: 605, 400, and 175 cm−1) that are considerably removed from the TO-mode frequencies computed from bulk single-crystal reflection data (BaTiO3: 510, 183, and 33.8 cm−1; SrTiO3: 546, 178, and 87.5 cm−1). These frequencies were successfully correlated with the bulk-crystal frequencies by use of classical electromagnetic scattering theory and an extension of Fröhlich's method. The low-frequency ``soft'' modes of both crystals were found to have an unusually large dependence on particle shape with the consequence that the powders absorb radiation at the corresponding LO-mode frequency.

Structural Studies of Potassium Hexatitanates Prepared under Hydrothermal and Solid State Conditions

“…al. have studied the effects of particle size and particle shape in the infra-red spectra of barium and scrontium titanate powders and showed that for small crystals, especially the fine powders, the departure from bulk mode frequencies may become quite large [13]. In this work, the different particle size and morphology of potassium hexatitanates (as seen in SEM results) were obtained from the different preparative conditions.…”

Infrared Absorption and Ferroelectricity of Small BaTiO3 Crystals

“…l a . The high frequency part of the spectrum is due to Last [3] and the extension t.0 frequencies below 300 em-1 is due to Luxon et al [4]. Since the observed absorption maxima do not agree with the Frohlich frequencies, we have calculated the extinction cross section from equation (8).…”

Raman and infrared spectroscopy of Na0.5Bi0.5TiO3 - BaTiO3 ceramics

“…As a result the Raman and also IR lines in ceramics resulting from the mode mixing and long range electrostatic force effects are relatively broader than that found in single crystals. The phonon frequencies also shift remarkably to higher/lower values depending upon the finite size of the powder grains and due to depelarization fields [27]. This can be the reason for the shifting of frequencies between the Raman and IR measurements.…”