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钒酸钇（ＹＶＯ４）是一种非常优良的双折射晶体。它不仅具有大的双折射值（０．２１，在１．３４μｍ下），而且易生长出大尺寸、高质量的晶体，同时也易加工镀膜。现今已逐渐取代方解石和金红石，在光纤通讯中作为光隔离器里的偏振楔形物以及在以可见光到红外（５μｍ）的光偏振器和分裂器上应用。从早期生长的ＹＶＯ４晶体透射光谱中发现在２．９μｍ波长附近有一个很宽的吸收峰。这是水和水致杂质（ＯＨ）－吸收所致。这将给在此波段范围内的晶体应用受到了限制。因此防止ＹＶＯ４原料合成及晶体生长过程中的水和水致杂质污染是十分必要的。ＹＶＯ４为金属氧化物，其原料或熔体在高温含水的气氛条件下，会引起高温水解作用生成氢氧作物：ＭＯ＋αＨ２Ｏ→ＭＯ１－α（ＯＨ）２α（１）或表示为：Ｏ２＋Ｈ２Ｏ→２（ＯＨ）－（２）在晶体生长过程中，这些氢氧化物即水致杂质（ＯＨ）－会不断地混入到晶体中引起了污染。因为水是无处不有并难以控制的杂质。因此我们尤其在原料烧结和晶体生长过程中除了尽力改善防水条件，例：原料放在隔离保纯炉内烧结防止潮湿气流入炉中，原料应保存在干燥器中。生长炉内保温材料防湿及炉壁干燥等均会减少（ＯＨ）－对ＹＶＯ４晶体污染但无法根除。防止（ＯＨ）－对?
Yttrium vanadate (YVO4) is a very good birefringent crystal. Not only does it have a large birefringence (0.21 at 1.34μm), it is also easy to grow large size, high quality crystals and is also easy to process. Nowadays, calcite and rutile have gradually been replaced, as polarization wedges in optical isolators and in optical polarizers and splitters using visible to infrared (5 μm). In the transmission spectra of YVO4 crystals grown in the early stage, it was found that there was a very broad absorption peak near the wavelength of 2.9 μm. This is caused by the absorption of water and water-borne impurities (OH). This will limit the use of crystals in this band. Therefore, to prevent YVO4 raw materials and crystal growth during the process of impurities in water and water pollution is necessary. YVO4 is a metal oxide, and its raw material or melt can cause high temperature hydrolysis to generate oxyhydrogen crop: MO + αH2O → MO1-α (OH) 2α (1) or expressed as O2 + H2O → 2 (OH ) - (2) These hydroxides, water-induced impurities (OH), continue to mix in the crystal causing contamination during crystal growth. Because water is ubiquitous and difficult to control. Therefore, we especially try our best to improve the waterproof condition during the process of raw material sintering and crystal growth. For example, the raw materials should be placed in an insulated pure furnace to prevent moisture from flowing into the furnace. The raw materials should be kept in the dryer. Growth of furnace insulation material moisture and furnace wall will reduce the drying (OH) - YVO4 crystal pollution but can not be eradicated. Prevent (OH) - right?