Investigation of Rare‐Earth Doped Barium Titanate

In this study the effect of additions of 0.0015 to 0.0030 mole fraction of rare‐earth oxides on the d.‐c. resistivity of sintered barium titanate was investigated. The substitution may be represented by ( X 2 O 3 ) M (BaTiO 3 ) 1‐M where X is the rare earth. The rare earths samarium, gadolinium, and holmium were introduced singly into the titanate, and the resistivity was measured as a function of temperature from −170° to +330°C. An anomalous increase near the tetragonal ‐ cubic transition temperature at 120°C. occurred which in some cases amounted to an increase in the resistivity of 4000 times the value in the tetragonal phase. The thermoelectric power of the material changed sign at the Curie temperature. The tetragonal phase exhibited n ‐type behavior whereas the cubic phase was p ‐type. The rhombohedra1 and orthorhombic phases exhibited conduction activation energies of the order of 0.2 e.v. whereas that in the tetragonal phase was approximately 0.1 e.v.