Complex Impedance Analyses of Ba_1-<i>_x</i>Li_0.5<i>_x</i>Bi_0.5<i>_x</i>TiO₃ Solid Solution PTCR Ceramics

Abstract

Conditions for the formation of (1- x )BaTiO 3 – x Li 0.5 Bi 0.5 TiO 3 (0 ≤ x ≤0.6) solid solutions with positive temperature coefficient of resistance (PTCR) effect were studied. Solid solutions were prepared by solid state reaction technique. Samples were sintered under reducing atmosphere N 2 /H 2 in the temperature range 1200–1450 °C with subsequent oxidation in air. The phase composition was investigated by X-ray powder diffraction method. It was found that samples of (1- x )BaTiO 3 – x Li 0.5 Bi 0.5 TiO 3 (0 ≤ x ≤0.6) solid solutions at room temperature exhibit perovskite structure. Unit cell parameters of unstable at the room temperature compound Li 0.5 Bi 0.5 TiO 3 were determined by extrapolation of concentration dependence of the unit cell parameters in the (1- x )BaTiO 3 – x Li 0.5 Bi 0.5 TiO 3 system. It was shown that minimum value of resistivity ρ min rises with increase in x value. Complex impedance method shown that ceramic grains of (1- x )BaTiO 3 – x Li 0.5 Bi 0.5 TiO 3 materials consist of three areas with different electrical properties. Boundary and outerlayer region of grains make the main contribution to the PTCR effect in lithium-containing solid solutions. It was shown that magnitude of the potential barrier's decreases with increasing x .