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Abstract
The investigation of impurity centres in BaTiO3 ceramics doped with rare-earth ions Y, La, Lu. Sm, and Dy with concentration 0·1-0·5 at.% were carried out by ESR methods at 160K<480K. It was shown that the most intense ESR lines belong to paramagnetic complex Fe3+-V0 and Ti3+-Ln3+ (Ln is rare-earth ion, V0 is oxygen vacancy). Exponential broadening of the ESR line of Fe3+-V0 centre in the tetragonal phase was observed. The origin of this broadening is discussed. Analysis of the obtained results along with conductivity data made it possible to find the characteristic concentration nc≈0·2-0·3 at.% of rare-earth ions: at n<ncor n>nc the rare-earth ions. except Lu, are substituted for Ba2+ or Ti4+ respectively. The role of this phenomenon as well as of the revealed paramagnetic centres in the appearance of positive temperature coefficient of resistivity is discussed.