機能素子を目指す単結晶育成の課題(<特集>機能素子・部品と単結晶育成)
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概要
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Taken up examples of crystal growth and evaluation of functional device materials are Gd_2(MoO_4)_3 and LiNbO_3 crystals. The Gd_2 (MoO_4)_3 crystal was grown as a high-quality crystal by measuring its unknown crystal structure, phase transition and phase relation and solving problems. In consequence, the crystal was found to be stoichiometric in composition and agree in congruent melt composition. However, the temperatuer difference from the eutictic temperature of that side of the composition rich in Gd_2O_3 is merely 7℃ and has an inclusion due to temperature variation. Further, because the three phases of α, β And β' are produced by phase transition, high-quality β'-Gd_2(MoO_4)_3 crystal cannot be obtained unless the cooling speed is accelerated. The LiNbO_3 crystal was developed as a substrate crystal for surface acoustic wave devices. To find congruent melt composition, sound speed was determined from the wafer whose upper part was made from the lower part of the crystal. Both sound speeds agree in congruent melt composition. Sound speed control is important, because the growth of large quantities of crystal unavoidably causes composition displacement.
- 日本結晶成長学会の論文
- 1990-11-15