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山大晶体所采用提拉法生长出新晶体铌酸钙钡。本文通过分光光度计和椭偏光谱仪分别测得室温下铌酸钙钡的透射率和折射率随波长的变化关系。透射率光谱显示该晶体在波长大于 380nm的可见光谱区是透明的。色散关系表明此材料的双折射较大 ,在短波区域寻常光及非常光的折射率之差约为 0 .1 2。此外 ,由透射率曲线计算了可见光范围内铌酸钙钡的吸收系数。从而得到吸收系数的平方根与光子能量的函数关系曲线。通过对该曲线的研究 ,发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁 ,计算出间接跃迁的禁带宽度Eg 以及声子能量EP。
Mountain crystal using the Czochralski method to grow a new crystal of calcium niobate barium. In this paper, the transmittance and refractive index of barium niobate at room temperature with the wavelength were measured by spectrophotometer and ellipsometer respectively. Transmissivity spectra show that the crystal is transparent in the visible region of the spectrum at wavelengths longer than 380 nm. Dispersion shows that this material has a large birefringence, and the difference between ordinary and extraordinary light in the short wavelength region is about 0.1 2. In addition, the absorption coefficient of barium niobate in the visible range was calculated from the transmittance curve. The square root of the absorption coefficient is thus obtained as a function of photon energy. Through the study of this curve, it is found that the corresponding transition below the absorption edge of barium niobate crystal is an indirect transition, and the forbidden band width Eg and the phonon energy EP of the indirect transition are calculated.