Dielectric characterization at high temperature of iron doped potassium strontium niobate ceramic by impedance spectroscopy
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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- δ showed superior to the permittivity values of the KSr2Nb5O15 host structure in all temperature range investigated. At room temperature, the permittivity values (2100) of KSr2(Fe0. 25Nb4. 75)O15- δ is two times the permittivity values of KSr2Nb5O15. The substitution of niobium cation by iron cation in the KSr2Nb5O15 host structure showed a suppression of the ferroelectric (P4bm) → paraelectric (P4/mbm) phase transition.
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Dielectric properties, Impedance spectroscopy, Niobate, Tetragonal tungsten bronze structure
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Inglês
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Materials Science Forum, v. 820, p. 187-192.
