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Nonstoichiometric BaTiO3 ceramics with 1 mole% MgO, 0.05 mol %
MnO2 and various amount of Sb2O3 and Y2O3 dopants are investi-
gated. Specimens fired with a rate- controlled sintering
profile exhibit a rather fine and uniform microstructure as
compared to those processed by conventional sintering
techniques. Curie tem- perature of BaTiO3-based ceramics is
shifted with the addition of Sb2O3 and/or Y2O3. Magnesium ions
acts as acceptors in the BaTiO3 lattice, while antimony, hence
the doped-BaTiO3 semicon- ductive region is shifted to higher
contents. Arrhenius plots of resistivity versus 1/εmT were
found to give straight lines for Tc<T<Tmax. The height of
potential ba- rriers at different temperatures, as calculated
from the slopes of these plots, were found to increase with
increasing Sb content. Plots of 1/εm vrsus temperature were
found to follow the Curie -Weiss law only within a small
temperature range (~60°C) above Curie temperature, giving a
second region with smaller slope. This behaviour can be
explained on the basis of the Heywang's model. The decrease of
the surface states at high temperature re- sults in the
narrowing of the grain boundary barrier layers.
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