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采用坩埚下降法生长了尺寸为φ12mm×70mm的0.80Na1/2Bi1/2TiO3–0.20BaTiO3(0.80NBT–0.20BT)无铅铁电单晶。通过X射线荧光分析研究了晶体中的分凝现象。结果表明:该单晶沿其纵向生长方向由顶部至底部,BaTiO3(BT)含量逐渐增加,晶体棒底部BT含量为32.15%(摩尔分数,下同),而顶部BT含量为14.26%。XRD分析表明:室温下晶体棒为四方相钙钛矿结构。随着BT含量增加,室温下晶体[001]方向的介电常数减小,去极化温度升高。位于晶体棒中间部位的晶体样品0.81NBT–0.19BT的压电性能最佳,室温下该样品在[001]方向的电学性能指标分别为:压电系数d33=158pC/N,机电耦合系数kt=0.463。
A 0.80Na1 / 2Bi1 / 2TiO3-0.20BaTiO3 (0.80NBT-0.20BT) lead-free ferroelectric single crystal with a size of φ12mm × 70mm was grown by the crucible descent method. The segregation phenomenon in the crystal was investigated by X-ray fluorescence analysis. The results show that the content of BaTiO3 (BT) gradually increases from the top to the bottom along the longitudinal growth direction of the single crystal. The content of BT in the bottom of the crystal rod is 32.15% (mole fraction) and the top BT content is 14.26%. XRD analysis shows that the crystal rod has tetragonal perovskite structure at room temperature. With the increase of BT content, the dielectric constant in [001] direction decreases and the depolarization temperature increases at room temperature. The piezoelectric properties of 0.81NBT-0.19BT in the middle of the crystal rod are the best. The electrical properties of the sample in the [001] direction at room temperature are: piezoelectric coefficient d33 = 158pC / N, electromechanical coupling coefficient kt = 0.463.