On the Electrical Conductivity of Some Alkaline Earth Titanates

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Abstract
The compounds Mg2TiO4, MgTiO3, MgTi2O5, CaTiO3, SrTiO3, and BaTiO3 were prepared in crystalline form by reactions in the solid state. The rod‐shaped samples were sintered in oxygen at 1450°C and reduced in hydrogen at temperatures from 560°C to 1400°C producing n type semiconductors. Resistivity values from 10−1 to 108Ω·cm at 25°C were obtained. Reductions of about 3 percent by weight could be given the most reduced magnesium titanates while the largest reduction obtainable in CaTiO3, SrTiO3, or BaTiO3 was less than 0.25 percent. The logarithm of resistivity was plotted versus reciprocal absolute temperature and showed a linear dependence in most cases over a wide range of temperature and resistivity. The curves for BaTiO3 changed the slope abruptly at approximately 115°C, probably attributable to the crystal structure change at the Curie temperature, about 120°C. The dependences of impurity activation energy and Fermi level on percent reduction were determined for the case of Mg2TiO4. The Biltz‐Meyer rule, stating a linear relationship of impurity activation energy with resistivity at a reference temperature, was not obeyed over the large range of reductions obtained.