引き下げ法によるLi_2B_4O_7単結晶の育成とその評価

概要

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Bubble-free, transparent Li_2B_4O_7 single crystals were grown by a newly developed pulling-down method. The use of a two-zone vertical furnace with a Pt-crucible realized a relatively steep temperature gradient of about 50°C/cm around the growth interface and a moderate gradient of about 13°C/cm below the interface, contributing to prevent grown crystals from cracking. Even at a pulling-down rate of 0.75 mm/h, which is higher than that in the Czochralski growth, the formation of bubbles was effectively suppressed at a rotation rate of 25 rpm. Any crystals grown along[110]direction involved no low-angle grain boundaries, but twinning was occasionally recognized. The dislocation density in the initial part of the crystal growth was found to be about 5 × 10^3/cm^2 from an etch pit pattern, while X-ray topography of a vertical cross section revealed that the number of dislocation lines decreased as the growth proceeded.
社団法人日本セラミックス協会の論文
1997-07-01