杂质对K2ZnCl4晶体无公度结构相变的影响

对K₂ZnCl₄铁电晶体在无公度-公度转变的相变点附近的孤子行为进行了研究。发现在相变点附近杂质使介电函数明显偏离居里-外斯定律,并导致介电峰值的明显下降;同时还发现杂质对升温相变点T_c^h较之对降温相变点T_c^c有更大的影响,这与Rb₂ZnCl₄等晶体中的情况恰好相反。采用朗道自由能理论可较好地描述杂质在相变点附近对介电函数的影响。分关键词：

EFFECT OF IMPURITIES ON INCOMMENSURATE PHASE TRANSITION OF K2ZnCl4 CRYSTAL

The soliton behavior of K₂ZnCl₄ crystal near commensurate-incommensurate phase transition point is investigated by dielectric measurement. It is found that the dielectric curve deviate from Curie-Weiss law and the dielectric peak value decrease with the increasing of the impurities. The influence of impurities on phase transition point T_c^h in heating run is larger than phase transition point T_c^c in cooling run. This phenomenon is contrary to the case of Rb₂ZnCl₄ crystal. The linear and nonlinear response of a multisoliton lattice is well described by a Landau-type theory. Analysis shows that the thermal hysteresis is mainly determined by the action of impurities, but this does not imply that the Peierls lattice pinning potential may not play any role in the thermal hysteresis.