Abstract
A DPT ferroelectric ceramics system of (Ba1-xLax)(Ti1-yZry)O3 and a DPT-SPT ferroelectric single crystal series of K0.2Na0.2(SrpBa1-p)0.8Nb2O6 have been studied. The dielectric constants as function of temerature of these materials have been measured. The semiquantitative point-analyses for composition distribution have been obtained by the technique of SEM and EDAX. The inhomogeneity of composition distribution was discovered in both DPT ceramics and crystal, but no such fluctuation was found in SPT crystal. This provided an experimental support to Smolensky's composition fluctuation model. The theoretical calculations of dielectric constant have been achieved by use of two kinds of form of ε'(T, Tc) and agree well with experiments.