【摘要】 在15～573K 温度范围内测量了铁电相铌酸锂单晶沿 c 轴方向的体电阻、介电常数、和热释电系数。数据表明在88、139、166、226、352、408和549K 附近,晶体性质出现特殊的变化。精确到0.4%的热释电测量表明在79.60℃温度上,自发极化强度 P_?和热电系数 dP_?/dT 连续,但 P_?对温度 T 的二次微商不连续;这与晶体中氧八面体旋转角的突变有关。从热释电测量发现,当晶体由85℃急冷至0℃时,晶体的转变出现延续时间超过80h的驰豫效应。在74～130K 之间,热电系数比例于爱恩斯坦比热函数。更多还原

【Abstract】 The pyroelectric constant,dielectric constant,and resistance of lithium niobatesingle crystal in the temperature range 15 to 573 K were measured.The data showedthat near 88,139,166,226,352,408 and 549 K the property change of ferroelectriccrystal appeared like phase transition.The pyroelectric measurement with accuracy0.4% showed that spontaneous polarization P and pyroelectric constant dP_s/dT were continuous,but d~2P_s/dT~2 was discontinuous at 79.60℃.This temperature is some-whathigher than 75℃,at which the crystal might undergo a transition related to the rota-tion of oxygen octahedra,as it was pointed out by other authors.When the crystalwas quickly cooled from 85° to 0℃,this transition took place with a long-lastingperiod more than 80 h.In the temperature range 74 to 130 K the pyroelectric constantwas proportional to Einstein’s specific heat function.更多还原