Abstract Far-infrared reflectivity spectra of bismuth germanium oxide (Bi12GeO20) single crystals are measured from room temperature down to 10 K. All the reflectivity spectra are fitted to a complex dielectric function $\varepsilon(\omega)$ in the factorised form. Phonon modes at low frequency are found to develop upon decreasing temperature and gain considerable spectrum weight below 150 K. The temperature-dependent static dielectric constants are obtained from the Lyddane--Sachs--Teller relation based on the obtained oscillator parameters. The dielectric constants are found to increase upon decreasing temperature, which is attributed to the charge transfer among the ions in the unit cell with the temperature varying.
Received: 27 April 2009
Revised: 21 May 2009
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant No 10674168) and Ministry
of Science and Technology,
China (Grant Nos 2006CB601006 and 2009CB930701).
Cite this article:
Muhammad Kamran, Dai Yao-Min(戴耀民), Ma Ji-Yun(马继云), Li Bo-Hong(李博宏), He Shi-Kun(何世坤), Zhang Wei-Jun(张伟君), Zheng Xiao-Rui(郑小睿), and Qiu Xiang-Gang(邱祥冈) Temperature-dependent far-infrared properties of Bi12GeO20 single crystal 2009 Chin. Phys. B 18 4425
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