Impedance spectroscopy of dielectric properties of perovskite ceramics Bi(Mg1/2Ti1/2)O3

The dielectric properties of metastable high-pressure perovskite ceramics Bi(Mg 1/2 Ti 1/2 )O 3 were studied by impedance spectroscopy at frequencies of 25 Hz-1 MHz at various temperatures. It is established that, at temperatures higher than ∼450 K, the dc conductivity makes a significant contribution to the dielectric response of these ceramics. The charge-carrier activation energy Δ E dc is found from the temperature dependence of the dc conductivity σ dc . As the temperature increases, the quantity Δ E dc changes in a jump from 0.12 to 1.00 eV at T ∼ 450 K. With inclusion of the contribution from σ dc , the real and imaginary parts ( M ac ′ and M ac ″ ) of the complex electrical modulus related only to the dielectric polarization are found. From analyzing the M ac ″ − M ac ′ diagrams, the contributions to the dielectric polarization from ceramic grains and their boundaries are estimated. The obtained data are interpreted in terms of the chemical composition of the ceramic compound Bi(Mg 1/2 Ti 1/2 )O 3 and the existence of crystal-lattice defects formed during the synthesis under pressure. Based on an analysis of the temperature dependences of the permittivity of ceramic grains and antiparallel displacements of the Bi 3+ cations, it is assumed that the dipole ordering in this perovskite compound is antiferroelectric in character.