Investigation on microstructure transition and electrical behavior in (1-x)Bi4Ti3O12/xBi4.5K0.5Ti4O15 lead-free composites

The lead-free (1- x)Bi ₄Ti ₃O ₁₂/ xBi _4.5K _0.5Ti ₄O ₁₅ composites ( x = 0–0.4) have been synthesized by solid state reaction method. Evolution of microstructure and electric properties has been investigated with varying composition ratio. X-ray diffraction, Raman and IR absorption confirm the crystal transition tendency from orthorhombic to tetragonal phase. Evident texture along c -axis crystallographic orientation is observed in structure and morphology characteristics with x = 0.05 and 0.1. Through modulating the mole ratio of Bi _4.5K _0.5Ti ₄O ₁₅ , coexistence of ferroelectric order and relaxor state is verified by the variation of ferroelectric hysteresis loops and polarization current density. This behavior can be attributed to the uncertain stability of discernable ferroelectric order induced by electric field among polar nanoregions during symmetry distoration. Temperature dependence of dielectric properties suggests an excellent thermal stability during a wide temperature range. Moreover, the detailed dielectric mechanism has been analyzed via various methods. Electrical conduction in grains and grain boundaries respectively plays the different role during the varying temperature process.