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Infrared active phonon modes and ionicity of single crystal MgAl2O4
毕聪志, 马继云, 颜俊, 方煦, 赵柏儒, 姚端正, 邱祥冈
2006 (5):
1090-1095.
doi: 10.1088/1009-1963/15/5/038
摘要
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Near-normal incident infrared reflectivity spectra of (100) MgAl2O4 spinel single crystal have been measured at different temperatures in the
frequency region between 50 and 6000cm-1. Eight infrared-active
phonon modes are identified, which are fitted with the factorized form of
the dielectric function. The dielectric property and optical conductivity of
the MgAl2O4 crystal are analysed. From TO/LO splitting, the
effective Szigeti charges and Born effective charges at different
temperatures are calculated for studying the ionicity and the effect of
polarization. Based on the relationship between the (LO--TO)1 splitting,
which represents the transverse and longitudinal frequencies splitting of
the highest energy phonon band in the reflectivity spectrum, and the
ionic-covalent parameter, the four main phonon modes are assigned.
MgAl2O4can be considered as a pure ionic crystal and its optical
characters do not change with decreasing temperature, so it may be used as a
suitable substrate for high-Tc superconducting thin films.
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