2006, Vol.16, No.4

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

The growth characteristics and properties of large size SrAlF5 single crystals are described and compared with those of BaMgF4. Transmission spectra in the vacuum ultraviolet wavelength region indicate a high transparency of SrAlF5 (about 90 % without considering surface reflection loses) down to 150 nm, on contrast to the optical loses observed for BaMgF4. The ferroelectric character of SrAlF5 is evidenced by the reversal of the spontaneous polarization in a hysteresis loop. The higher potential of SrAlF5 in comparison with BaMgF4 for the realization of all-solid-state lasers in the ultraviolet wavelength region by the quasi-phase matching (QPM) technique is pointed out. SrAlF5, besides a higher grade of transparency, shows a nonlinear effective coefficient similar to that of quartz and uniaxial nature, on contrast to the one order smaller nonlinear coefficient and biaxial character of BaMgF4. The refractive index of SrAlF5 from the ultraviolet to the near-infrared wavelength region is measured by the minimum deviation method. The Sellmeier and Cauchy coefficients are obtained from the fits to the curves of the ordinary and extraordinary refractive indices, and the grating period for the first order QPM is estimated as a function of the wavelength. The poling periodicity for 193 nm SHG from 386 nm is 4 mm.Key words Fluoride, SrAlF5, BaMgF4, Ferroelectric, Nonlinear optics, UV, SHG1. Introduction

Skull melting method can be a good candidate for growing oxide single crystals with high quality and for mass production because of its low production costs and high yield through recycling of crust. In this study, rutile single crystals were grown by the skull melting method and ingot characteristics with the variation of different growth conditions has been investigated. Conditions for high quality rutile ingot growth were used for producing cold-crucible size of ?12 cm×H14cm, capacity of 3000 pF tank condenser, work frequency of 2.84 MHz, melt-dwelling time of 9hrs and growing speed of 2 mm/h.Key words Skull melting, Rutile single crystal, Rutile ingot, Cold-cruclble루틸단결정 성장을 위한 스컬용융시스템의 조건석정원?, 최종건*동신대학교 보석공학과, 나주, 520-714*세라믹공정연구센터, 서울, 133-791(2006년 5월 30일 접수)(2006년 6월 15일 심사완료)

For an aspect ratio (transport length-to-width) of 5, Pr = 2.89, Le = 0.018, Pe = 2.29, Cv = 1.11, PB = 40 Torr, solutally buoyancy-driven convection (Grs = 3.03 ? 105) due to the disparity in the molecular weights of the component A (Hg2Cl2) and B (He) is stronger than thermally buoyancy-driven convection (Grt = 1.66 ? 104). The crystal growth rate is decreased exponentially for 2.5 ? Ar ? 5, with (1) the linear temperature profile and a fixed temperature difference, (2) the imposed thermal profile, a fixed crystal region and varied temperature difference. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. But, with the imposed thermal profile, a fixed source region and varied temperature difference, the rate is increased for 2 ? Ar ? 3, and remains nearly unchanged for 3 ? Ar ? 5.Key words Mercurous chloride, Solutally buoyancy-driven convection, Aspect ratio, Physical vapor transport1. Introduction