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J. Korean Ceram. Soc. > Volume 28(12); 1991 > Article
Journal of the Korean Ceramic Society 1991;28(12): 981.
인상 육성한 $Bi_12GeO_20$ 결정내의 $Bi_4Ge_3O_12$석출상
이태근, 정수진
서울대학교 공과대학 무기재료공학과
Exsolution of $Bi_4Ge_3O_12$ in $Bi_12GeO_20$ Crystals Grown by Pulling Method
Various crystal defects such as voids, inclusions dislocations, stacking faults and precipitates were observed in the Czochralski-grown Bi12GeO20 crystals. Particularly, precipitates were found in the whole crystals. The phase of these precipitates was identified as Bi4Ge3O12 by EPMA and transmission electron microscopy. The precipitates were produced by pulling rapidly from a non-stoichiometric charge. During the pulling of Bi12GeO20 crystals, the melt composition of stoichiometric charge was changed Bi-deficent with gradual volatilization of Bi2O3. Precipition of the second phase may have been affected by an abrube thermal stress. By adding excess Bi2O3 into the stoichiometric batch, the precipitation of Bi4Ge3O12 was suppressed. At a pulling speed of 2 mm/hr, clear and precipitate from crystals of Bi12GeO20 were grown from the melt of the Bi2O3 excess charge.
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