A study was made of the synthesis and conductivity of Al- and Ga-substituted ””-ferrites. Substitution of Al or Ga in K2O•9.75(Fe1-xMex)2O3•2.5CdO was possible for x-values of up to 0.2, and up to 0.4, respectively. It was found that there was an isotropic decrease in the lattice constant, of 1%, for an Al substitution of 0.2. There was an anisotropic decrease, of 0.75%, in the case of Ga substitution. The bulk ionic conductivity of Al-substituted ferrite was equal to 3.0S/m at 250C, for an x-value of 0.2. This was slightly lower than the value before substitution. The grain boundary conductivity of the Al-substituted ferrite increased up to 0.61S/m at 250C, for an x-value of 0.2. This was about 17 times higher than the value before substitution. The bulk ionic conductivities of the Ga-substituted ferrites were almost the same as those of the Al-substituted ferrites.

H.Takamura, T.Kagotani, T.Tanaka, M.Homma, M.Okada: Materials Transactions, 1996, 37[4], 796-800