Redox behavior and electrical properties of Sr and Zr substituted BaTiO sub(3)

The oxidation and reduction behavior of Sr and Zr substituted BaTiO sub(3) has been studied by measuring equilibrium electrical conductivities as a function of oxygen activity. The substitution of Sr super(+2) and Zr super(+4) for Ba super(2+) and Ti super(4+) in BaTiO sub(3) shifted the conductivity profiles to lower oxygen partial pressures. The replacement of Ba with smaller Sr ions suppresses the oxygen dissociation from the lattice, consequently increasing the enthalpy for reduction ( Delta H sub( )n, whereas the Sr substitution requires less energy for oxidation ( Delta H sub( )p. The increase in reduction enthalpy at lower oxygen activities suppresses the formation of oxygen vacancies, the materials becoming resistant to reduction process. Such a reduction resistant behavior gave rise to greater electrical resistivities for (Ba sub(0.9)Sr sub(0.1))(Ti sub(0.9)Zr sub(0.1))O sub(3) than for Ba(Ti sub(0.9)Zr sub(0.1))O sub(3) when the samples were sintered at lower P(O sub(2)).