Low-temperature dielectric behavior of Sc- and In-doped bismuth titanate pyrochlores

The detailed structural description and analysis of dielectric behavior of Bi1.6MxTi2O7-delta (M - Sc, In; x = 0.2, 0.4, 0.6) compositions are demonstrated. Doping results in cation disorder either in A-site (x = 0.2, 0.4) or A-,B-sites (x = 0.6) of pyrochlore. The displacements of the A-site atoms and O ' from the ideal sites are shown. For both dopants, the maximum dielectric constant epsilon ' was 98, and the dielectric losses remain reasonably close to the values below 0.0058 at x = 0.4, 25 degrees C, 1 MHz. A drop of epsilon ' is observed at the other dopants concentrations. With the dopant content rising, the temperature coefficient of capacitance (TCC) increases and is positive (579 divided by 782 ppm/degrees C) below room temperature (RT) and then becomes negative (-49 divided by -220 ppm/degrees C) above RT. The revealed low-temperature relaxation process could be associated with jumps of the A-ions within the A(2)O ' substructure.