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Analyses of the Raman Spectra of the Incommensurate Ferroelectrices RB(2)ZNCL(4) and K(2)SEO(4).

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Previously, a study 1 of the Raman spectrum of the incommensurate ferroelectric, potassium selenate K2SeO4 was reported. A qualitative model was proposed in that work to explain the universal observation, that in its paraelectric phase, there is a higher multiplicity of lines in the internal mode spectra selenium-oxygen vibrations within the selenate tetrahedra than predicted. More recently in addition to refining some of our measurements of the selenate spectra, we have made a detailed study and analysis of the Raman spectra of an isomorph of K2SeO4, rubidium tetrachlorozincate RbZnCl4, also known like K2SeO4, to exhibit incommensurate behavior. This experimental study paralleled and reinforced an intensive theoretical study of the lattice dynamics of RbZnCl4, to be described elsewhere, but from which calculated Raman peak frequencies were taken and are cited in this report. In the following sections, we describe our experimental results on RbZnCl4, our analytical procedures, and the results of our analysis, and we compare these results with our earlier studies on K2SeO4 and with the predictions of the model offered previously and described briefly above. We also present in a second chapter some new measurements of the potassium selenate internal mode spectra, made with more precise frequency calibration, for comparison with work reported by other laboratories.

Subject Categories:

  • Crystallography
  • Electricity and Magnetism
  • Atomic and Molecular Physics and Spectroscopy

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