STUDY OF OCCUPATIONAL SITES AND DIELECTRIC PROPERTIES OF Ho-Mg AND Ho-Mn SUBSTITUTED BaTiO3

The effect of reoxidation treatment on the solubility in dopants and the dielectric properties of Ho-Mg- and Ho-Mn-substituted BaTiO3 was investigated. The lattice parameter and electrical resistivity results indicated that the predominant occupational sites of Ho ions changed from A-sites to B-sites by increasing the doped content in both systems. In the case of Ho-Mn-substituted samples, the decrease in lattice parameter and a shift of the Curie point to higher temperatures by reoxidation treatment were observed in the range in which Ho ions predominantly occupy B-sites (act as acceptors). On the other hand, Ho-Mg-substituted samples showed little change. ESR measurements revealed that these changes due to reoxidation were based on the decrease of the ionic size of Mn due to the oxidation of Mn2+ to Mn3+ or Mn4+. The occupational sites of Ho ions strongly affected the valence state of Mn and the dielectric properties of BaTiO3. 10 refs.