Structure and Dielectric Behavior of Yb(2)O(3)-MgO Co-Doped 0.92BaTiO(3)-0.08(Na(0.5)Bi(0.5))TiO(3) Ferroelectric Relaxor

Dielectric properties and structure of 0.015Yb(2)O(3)-xMgO doped 0.92BaTiO(3)-0.08(Na(0.5)Bi(0.5))TiO(3) ceramics with x = 0.0–0.025 have been investigated. As Yb(2)O(3)-MgO was added into the BT-NBT, the phase changes from tetragonal to pseudo-cubic, with the tetragonality c/a 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 (ε(r)′~2300) appears in the temperature dependent dielectric constant curve (ε(r)′-T), which produces a flat ε(r)′-T curve. Sample 0.92BaTiO(3)-0.08(Na(0.5)Bi(0.5))TiO(3)-0.015Yb(2)O(3)-0.005 MgO and 0.92BaTiO(3)-0.08(Na(0.5)Bi(0.5))TiO(3)-0.015Yb(2)O(3)-0.01MgO give a ε(r)′ variation within ±14% and ±10% in 20–165 °C. The core–shell microstructure should take account for the flattened ε(r)′–T behavior of these samples.