Microstructural and Electrical Properties of Barium Strontium Titanate and Nickel Zinc Ferrite Composites

摘要

Structural and electrical properties of oxide composite of two ferroic ternary Ba_(0.6)Sr_(0.4)TiO3 and Ni_(0.5)Zn_(0.5)Fe2O4 were investigated. Powder x-ray diffraction studies show that the end products, BST possess cubic perovskite structure and NZF possess cubic spinel structure. A very systematic phase transition between these two phases has been achieved for intermediate doping ranges. Surface morphology revealed a uniform grain distribution with very low porosity for entire composite series. Real and imaginary permittivity and loss tangents for all the composites up to 1 MHz frequency range show high dielectric constants and low losses, respectively. Exceptionally, high dielectric permittivity values were obtained for composite samples as compared to pristine end products. At lower frequencies, the values of dielectric permittivity were high, because the excitation of bound electrons, lattice vibration, dipole orientation and space charge polarization are active. At high frequencies, the dielectric permittivity exhibited frequency independence behavior for entire series. AC conductivities determined from the dielectric data exhibited strong frequency dependence with a non linear increase with increasing frequencies. The electrical conduction in the system may be modeled by hopping model.