Electrical properties and positron annihilation study of (Ba1–xHox)TiO3 ceramics

DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1–xHox)TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1–xHox)TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ~1,300 to ~4,000), with only a slight increase in the corresponding dielectric loss. The local electron density and defect concentration estimated using positron annihilation technique conforms well to the features found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model.