Dielectric Characterization at High Temperature of Iron Doped Potassium Strontium Niobate Ceramic by Impedance Spectroscopy

Abstract

Tetragonal Tungsten Bronze structure TTB-type structure has attracted interest by the high anisotropy of the crystal structure. The dielectric characterization of iron-doped niobate of TTB-type structure, with stoichiometry KSr2(Fe0.25Nb4.75)O15-δ, prepared by Modified Polyol Method was investigated. Nanocrystalline single phase powders were obtained after calcination of the precursor powder at 1150 °C for 10 hours in an oxygen atmosphere. The dielectric characterization was performed by impedance spectroscopy, from room temperature to 600 °C, in the frequency range of 5 Hz to 13 MHz. The permittivity values obtained for KSr2(Fe0.25Nb4.75)O15-δshowed superior to the permittivity values of the KSr2Nb5O15host structure in all temperature range investigated. At room temperature, the permittivity values (2100) of KSr2(Fe0.25Nb4.75)O15-δis two times the permittivity values of KSr2Nb5O15. The substitution of niobium cation by iron cation in the KSr2Nb5O15host structure showed a suppression of the ferroelectric (P4bm)→paraelectric (P4/mbm) phase transition.