Two stoichiometric compositions are known for this compound; Bi12GeO20 with a molar ratio of 6 Bi2O3:l GeO2 and Bi4Ge3O12 with 2 Bi2O3: 3 GeO2. Bismuth germanate, Bi12GeO20, has been grown as large single crystals, using the Czochralski technique, by several investigators, including Ballman and Lauer, Aldrich et al., Dickinson et al. It is strongly piezoelectric, optically active, photoconductive and shows a small linear electrooptic effect. A practical advantage of this material is its low melting point, (918°C), which allows the preparation of mechanically sound crystals more easily than other electro-optic crystals with higher melting points. The phase diagram has been published by Speranskaya and Arshakuni.
KeywordsAcoustic Surface Wave Optical Activity Bismuth Oxide Large Single Crystal Linear Birefringence
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