Electrical Properties of Nd-Doped BaTiO3 PTC Ceramics Prepared by Hydrothermal Synthesis

Nd-doped BaTiO3 nanopowders with ca. 200 nm in average diameter were prepared by hydrothermal synthesis at 200 and 240 degrees C for 24 h. Neodymium (III) nitrate hexahydrate (Nd(NO3)(3)center dot 6H(2)O) as a donor dopant was added to the powder mixtures of barium hydroxide (Ba(OH)(2)) and titanium dioxide (TiO2) ranging from 0.25 to 0.45 mol%. A green compact of the powder mixtures obtained was heated at 1340 degrees C for 2 h with/without three steps of ramp heating processes. Sintered without these steps, 0.35 mol% Nd-doped BaTiO3 with the resistivity of 124 ohm. cm at R. T. indicated insufficient PTCR effect; resistance change of 3 x 10(2) in the vicinity of Curie temperature. On the other hand, a pellet of 0.35 mol% Nd-doped BaTiO3 sintered via the step-heating process exhibited the large resistance change of 7.5 x 10(3).