NBT-KBT-BT系弛豫铁电体的弥散相变研究

Investigation on Diffuse Phase Transition of NBT-KBT-BT Ferroelectric Relaxors

采用传统压电陶瓷固相合成法制得纯钙钛矿相的(1.002-5x)NBT-4xKBT-(x-0.002)BT(x=0.026,0.028,0.030,0.032,0.034)(简写为BNBKT100x)系弛豫铁电体。通过X-射线衍射(XRD)分析,当x=0.030时为三方、四方两相共存,为该体系的准同型相界。系列样品的介电温谱显示在室温到500℃之间存在两个介电反常峰,分别对应于陶瓷材料的铁电-反铁电-顺电相变。同时发现该系列样品显示出弛豫铁电体特性。并用成分起伏理论解释了这种弛豫弥散相变。

（1. 002 -- 5x） NBT-4x KBT-（x- 0. 002） BT （x = 0. 026,0. 028,0. 030,0. 032,0. 034） （abbr. as BNBKT100x） lead-free ceramics systems were prepared by conventional solid-state ceramics preparation method. XRD resust show that the crystalline structure of the investigated materials were single perovskite. The morphotropic phase bounday （MPB）of the system between rhombohedral and tetragonal locates about at x=0. 030. The dielectric properties of BNBKT100x samples from room temperature to 500 ℃ at different frequencies and at 1 kHz were studied . Two dielectric constant abnormal peaks exists,which corresponding to the phase transition of ferroelectric to antiferroelectric and antiferroelectric to paraelectric phase. It was also found that in the compositions thus prepared were all ferroelectric relaxors. And the causes of diffuse phase transition were interpreted by The theory of heterophase fluctuation .