Structure and Dielectric Behavior of YbO-MgO Co-Doped 0.92BaTiO-0.08(NaBi)TiO Ferroelectric Relaxor.

Dielectric properties and structure of 0.015YbO-MgO doped 0.92BaTiO-0.08(NaBi)TiO ceramics with = 0.0-0.025 have been investigated. As YbO-MgO was added into the BT-NBT, the phase changes from tetragonal to pseudo-cubic, with the tetragonality / decreases from 1.011 to 1.008 and XRD peaks broadened. The combined study of XRD and TEM image revealed a formation of core-shell structure in grains with core of 400-600 nm and the shell of a thickness 60-200 nm. There is a slowly phase transition against temperature from the variable temperature Raman analysis. The ferroelectric relaxor peak of BT-NBT decreases from 4000 to ~2000 and a new broad dielectric peak with an equivalent maximum ('2300) appears in the temperature dependent dielectric constant curve ('-), which produces a flat '- curve. Sample 0.92BaTiO-0.08(NaBi)TiO-0.015YbO-0.005 MgO and 0.92BaTiO-0.08(NaBi)TiO-0.015YbO-0.01MgO give a ' variation within ±14% and ±10% in 20-165 °C. The core-shell microstructure should take account for the flattened '- behavior of these samples.