Dielectric relaxation in Ba(Y_(1/2)Nb_(1/2))O_3-BaTiO_3 ceramics

摘要

Lead-free (1 - x)Ba(Y_(1/2)Nb_(1/2))O_3-xBaTiO_3;(0 ≤ x ≤ 1) ceramics have been synthesized using solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies. The crystal-structure of the compounds is found to be cubic with the space group Pm3m(221) except for BaTiO_3 for which it is tetragonal (P4/mmm). Complex impedance spectroscopy analysis indicated the presence of non-Debye type dielectric relaxation in Ba(Y_(1/2)Nb_(1/2))O)3-BaTiO_3 system. Compound 0.25Ba(Y_(1/2)Nb_(1/2))O_3-0.75Ba-TiO_3 exhibited a low value of temperature coefficient of capacitance (＜±8 %) in the working temperature range (up to +100 ℃), room temperature dielectric constant equal to 295 and low loss tangent (0.039) which meets the specifications for "Z5F" of Class I dielectrics of Electronic Industries Association. Hence, this composition might be a suitable candidate for capacitor applications. Ac conductivity and electric modulus studies supported the hopping type of conduction in the system and frequency dependent ac conductivity data obeyed Jonscher's power law.