Effect of donor dopants cerium and tungsten on the dielectric and electrical properties of high Curie point ferroelectric strontium niobate

The perovskite-like layered structure (PLS) A₂B ₂O₇ compound Sr₂Nb₂O₇ was doped with donor dopants CeO₂ and WO₃ to explore their doping effect on its A and B site, respectively. The doped ceramics were prepared by Spark Plasma Sintering. For Ce doping on the A site, single phase was maintained up to 5 mol% Ce (x=0.05 in (Sr_1-xCe_x) ₂Nb₂O₇). For W doping on the B site, single phase was maintained at 2.5 mol% W (x=0.025 in Sr₂(W _xNb_1-x)₂O₇). The cerium and tungsten doping both inhibited grain growth and changed the grain morphology, leading to less anisotropic grains. The Curie point T_c was obtained by measuring the temperature dependence of the dielectric constant and it was found to reduce for both Ce and W doped SNO. The W doped ceramics showed a diffuse ferroelectric phase transition at the Curie point. The DC resistivity of tungsten and cerium doped SNO increased compared to undoped SNO at temperatures below 700° C. These results showed that both Ce and W had a strong influence on the dielectric and electrical properties of the Sr₂Nb ₂O₇ ceramics.