钙钛矿型铁电体位移型相变的序参量

位移型相变是一种对称破缺的连续相变．对称性的变化反映了晶体内部有序化程度的改变，序参量应该能够很好地说明这种变化，居里原理将两者紧密地联系起来．已知相变前后对称性的变化，由居里原理可求出序参量的对称性．钙钛矿型铁电体发生位移型相变有两种方式．对于阳离子位移的情况，选择自发极化矢量作为序参量；对于氧八面体扭转的情况，选择四偶极张量作为序参量．

Order Parameter of Perovskite Ferrectrics in Displacive Phase Transition

Displacive phase transition is a kind of continuous phase transition of symmetry breaking. Changes of symmetry reflect the changes of orderly degree in crystals, order parameter should be able to explain this changes per- fectly. Symmetry and order parameter are closely contacted by Curie's principle. If the changes of phase transition is known, the symmetry of order parameter can be drawn using Curie's principle. Perovskite ferroelectrics have two forms in displacive phase transition. In the case of positive ions displaced, spontaneous polarization is choosen as order parameter; the case that oxygen octahedrons are rotated, quadrupole tensor is slected.