Optical and dielectric properties of nanosized ceramics Bi2Mg1-xСrxTa2O9.5-Δ with pyrochlore structure

Chromium-containing pyrochlores Bi2Mg1-xСrxTa2O9.5-Δ with a variable content of magnesium / chromium ions were obtained by solid-phase synthesis. The synthesized samples characterized loose nanosized microstructure formed partially intergrown ceramic grains. They bright green. With an increase in the samples, unit cell parameter solid solutions decreased from 10.4890 to 10.4467 Å, obeying Vegard’s rule. absorption spectra contained several features range below 400 nm, shoulder 450 – 520 broad 600 700 nm maximum at 650 and narrow peak 724 nm. band gap materials for direct allowed most intense electronic transitions was 2.14 2.29 eV. At 23°С, permittivity wide frequency (102 –106 Hz) practically independent increasing 19.5 16.5 106 Hz. Above 105 Hz, dielectric loss tangent all slightly depended on took low values 0.004 (106 Hz). conduction activation energy varied 1.39 ÷1.48