MICROSTRUCTURE AND DIELECTRIC CHARACTERISTICS OF (PBXBA0.5-XSR0.5)TIO3 CERAMICS

Microstructural and dielectric properties of the PbxBa0.5-x-Sr0.5TiO3 system have been studied, It is found that this system forms a solid s olution in the entire composition range (0.01 less than or equal to x less than or equal to 0.5) and is cubic for the x = 0, 0.1, and 0.2 co mpositions and tetragonal for other compositions, Measurements of the dielectric constant as a function of temperature reveal that this mate rial is ferroelectric at room temperature for the x > 0.2 compositions and has a broad paraelectric-ferroelectric transition region, No shif t in the dielectric maxima was noted; however, there is a slight sprea d in the dielectric constant with frequency for the x = 0.4 compositio n, A quantitative model to mathematically analyze the effect of compos ition fluctuations on the dielectric broadening for a ternary system i s presented, Transmission electron microscopic studies reveal the pres ence of 90 degrees ferroelectric domains oriented along the {01(1) ove r bar} planes for the x = 0.3 and 0.4 compositions.