Suppression of ferroelectric phase-transition in niobates via solid solution formation

Suppression of the phase-transition type ferro-paraelectric from doping of KSr2Nb5O15 host-structure was investigated by set of techniques X-ray diffraction, Mossbauer spectroscopy and Dielectric spectroscopy at high temperature. High crystalline and single phase iron-doped niobate ceramic with Tetragonal Tungsten Bronze TTB-type structure, stoichiometry KSr2(FeNb4) O15-delta, was prepared by conventional technique using high energy milling. Both techniques Rietveld Method and Mossbauer spectroscopy showed that Fe3+ cations occupy two different octahedral sites in the TTB structure on the niobium octahedral sites, termed as Nb(1) and Nb(2). At room temperature, the dielectric permittivity value of the KSr2(FeNb4) O15-delta is two times higher than the permittivity values of the KSr2Nb5O15. The suppression with extinction of ferro-para phase-transition occurs as function of break-down of polar characteristic. New non-polar space group development stemming from solid solution formation is discussed. (C) 2019 Elsevier B.V. All rights reserved.