Stoichiometric and Nonstoichiometric Compounds
authors Tkach, A; Vilarinho, PM
editors Tanasescu, S.
chapter title Nonstoichiometry Role on the Properties of Quantum-Paraelectric Ceramics
nationality International
author keywords nonstoichiometry, perovskite, electroceramics, ferroelectrics, crystallographic phase assemblage, grain growth, dielectric spectroscopy
abstract Among the lead-free perovskite-structure materials, strontium titanate (SrTiO3 - ST) and potassium tantalate (KTaO3 - KT), pure or modified, are of particular importance. They are both quantum paraelectrics with high dielectric permittivity and low losses that can find application in tunable microwave devices due to a dependence of the permittivity on the electric field. Factors as Sr/Ti and K/Ta ratio in ST and KT ceramics, respectively, can alter the defect chemistry of these materials and affect the microstructure. Therefore, if properly understood, cation stoichiometry variation may be intentionally used to tailor the electrical response of electroceramics. The scientific and technological importance of the stoichiometry variation in ST and KT ceramics is reviewed and compared in this chapter. The differences in crystallographic phase assemblage, grain size and dielectric properties are described in detail. Although sharing crystal chemical similarities the effect of the stoichiometry is markedly different. Even if the variation of Sr/Ti and K/Ta ratios did not change the quantum-paraelectric nature of ST and KT, Sr excess impedes the grain growth and decreases the dielectric permittivity in ST ceramics, while K excess promotes the grain growth and increases of the dielectric permittivity in KT ceramics.
publisher IntechOpen
year published 2019
book digital object identifier (doi) 10.5772/intechopen.89499
file inthech69496_tkach_vilarinho.pdf
link https://www.intechopen.com/online-first/nonstoichiometry-role-on-the-properties-of-quantum-paraelectric-ceramics


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