Influence of Structure on Curie Weiss Constant of [(Pb1-x Srx)1-1.5zLaz ]TiO3 Ceramics

Theoretical studies have been carried out to reveal the proper concentration of Sr and La-content which provide the samples of [(Pb1-x Srx )1- 1.5zLaz ] TiO3 ceramics with optimum ferroelectric properties and to find an interpretation for the behavior of the Curie Weiss constants (C- , C+ ). In this work, three types of samples were considered according to the concentration of La-content. The frequency of electric field used in dielectric measurements equal 1KHz. From the relation between Curie Weiss constants and Sr content , the samples of first type (z =3 mole % La) exhibited two minimum values for (C- , C+ ) at x= 20 and 40 mole %Sr. The samples of second type(z= 6 mole%La) showed a similar behavior but the minimum values for (C- , C+ ) at x= 25 and 35 mole %Sr. The samples of third type (z=9 mole %La) were characterized with only one minimum value for (C- , C+ ) at x= 30 mole %Sr. In this paper ,we concluded that at a constant concentration of Sr content ( 26mol%) or Pb content (60.5mol%) both values of Curie- Weiss constants (C- , C+ ) and εmax increase with increasing of La content. This remark is a unique phenomenon for the behavior of Curie-Weiss constants (C- , C+ ). The interpretation of the behavior of Curie- Weiss constants (C- , C+ ) for the samples is attributed to the types of unit cells which are dominated in structure.