科研之友
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摘要
High-pure, single-phase, free of voids and high mass density AgGaS2 polycrystalline was synthesized by a new method, i.e. two-temperature zone vapor-transporting together with the mechanical and melt temperature oscillation method (TVMMTOM), directly from high-purity (6 N) elements silver, gallium and sulfur with excess sulfur. The mechanism and advantages of the new method for synthesizing high-quality AgGaS2 were discussed. It is found that the polycrystalline material synthesized by the new method is superior to that synthesized by the conventional method, what is more the new method can avoid the explosion of the synthetic quartz ampoule. Adopting the modified Bridgman method an integral and crack-free AgGaS2 single crystal with diameter of 14 mm and length of 63 mm has been obtained. It was found that there was a (1 0 1) cleavage face and the four order X-ray spectrum of the (1 0 1) faces was observed. By the method of DSC analysis the melting and freezing points of the AgGaS2 single crystal were about 995 and 955 degrees C. The transmission spectra of the AgGaS2 sample of 10 x 8 x 2 mm(3) were obtained by means of UV and IR spectrophotometer. The limiting wavelength was 470 nm and the band gap was 2.64 eV. It can be found in the infrared spectrum that the infrared transmission was above 55% from 4000 to 800 cm(-1), and the infrared transmittance of the crystal is up to 63% at 10.6 mu m. which is higher than that of the crystal grown using polycrystalline materials synthesized by the conventional method. The value of alpha in 10.6 mu m was 0.267 cm(-1). Above mentioned results showed that the crystal was of good quality and TVMMTOM is preferable for synthesizing high-quality AgGaS2 polycrystalline materials.
