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在500Hz 至13MHz 的频率范围内,测量了Cd_(0.03)Sr_(0.485) Ba_(0.485)Nb_2O_6晶体的新鲜试样以及经过强交流电场处理的试样的介电谱。结果表明,新鲜晶体试样中存在低频弛豫机构,经过强的交流电场处理后这一弛豫机构消失,而且晶体的交流电导率也降低一个数量级。我们还研究了偏置电场对介电常数温度依赖性的影响,发现偏置电场使介电常数呈现极大渔的温度Tm向高温方向移动,而且使Tm附近介电常数的值减小。前者可由扬致相变加以解释,后者表示此晶体的铁电-顺电相变可能是二级的。另外,实验结果表明,在本工作的测试范围内,偏置电场对本晶体相变的弥散性没有影响。
The dielectric spectra of fresh samples of Cd_ (0.03) Sr_ (0.485) Ba_ (0.485) Nb_2O_6 crystals and those of samples subjected to strong AC electric field were measured in the frequency range from 500Hz to 13MHz. The results show that there is a low-frequency relaxation mechanism in the fresh crystal sample, and the relaxation mechanism disappears after strong AC electric field treatment, and the AC conductivity of the crystal is reduced by an order of magnitude. We also study the effect of bias electric field on the temperature dependence of dielectric constant. We find that the biased electric field moves the temperature Tm at which the dielectric constant shows great fishing to the high temperature, and decreases the dielectric constant near Tm. The former can be explained by the induced phase transition, which indicates that the ferroelectric-paraelectric phase transition of this crystal may be secondary. In addition, the experimental results show that in the scope of this work, the bias field has no effect on the dispersion of the crystal phase transition.