A. C. Impedance Analysis on b-axis Oriented Ba_1-xSr_xTi₂O₅ Prepared by an Arc-Melting Method

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Dielectric properties of SrO substituted BaTi₂O₅, Ba_1-xSr_xTi₂O₅ prepared by arc melting were investigated. Due to the thermal instability of BaTi₂O₅ at high temperatures, the decomposition of BaTi₂O₅ was accompanied with solid solution of SrO in BaTi₂O₅. Lattice parameters of Ba_1-xSr_xTi₂O₅ decreased with increasing SrO, and the solubility limit of SrO in Ba_1-xSr_xTi₂O₅ was about x=0.12. A small amount of second phases of BaTiO₃ and Ba₆Ti₁₇O₄₀ were identified at x<0.12 by scanning electron microscopy. Ba_1-xSr_xTi₂O₅ showed a strong b-axis orientation. The Curie temperature (T_c) of Ba_1-xSr_xTi₂O₅ changed in the range between 703 and 750 K depending on SrO content. The dielectric permittivity of Ba_1-xSr_xTi₂O₅ at the T_c was attained to 2700 by substituting SrO of x=0.03. The electrical conductivities of Ba_1-xSr_xTi₂O₅ were lower than that of non-substituted BaTi₂O₅. Ba_1-xSr_xTi₂O₅ containing the second phases showed distorted Cole-Cole semicircles which were deconvoluted into two semicircles based on a Maxwell-Wagner model corresponding to a ferroelectric bulk matrix and paraelectric second phases.