On the Relation of the Order-Parameter and Transition Temperature in Ferroelectric Solid Solutions

Within the framework of the model of coupled anharmonic oscillators a ferroelectric solid solution is described with only a few parameters. In high-temperature approximation a linear relation between the square of the order parameter and the transition temperature is obtained. This is illustrated by an application to several modified lead titanate ceramics, the linear relation between transition temperature and tetragonal lattice deformation is verified. For tris-sarcosine calcium chloride (bromide) (TSCC/B) at very low temperatures the expected deviation from the classical behaviour is seen.