Oxygen vacancy-related dielectric relaxation and electrical conductivity in La-doped Ba(Zr sub(0.9)Ti sub(0.1))O sub(3) ceramics

Ba sub(1-x)La sub(x) (Zr sub(0.9)Ti sub(0.1)) sub(1-x/4)O sub(3) (BLZT) ceramics with x = 0.02 (BLZT-1), 0.04 (BLZT-2), 0.06 (BLZT-3) and 0.08 (BLZT-4) were prepared by a solid-state reaction route. Crystal structure of the BLZT ceramics was determined using X-ray diffraction and Raman spectroscopy. While the ceramics for x less than or equal to 0.04 are pure phase with cubic perovskite structure, pyrochlore La sub(2)Zr sub(2)O sub(7) appears in the samples with x = 0.06 and 0.08. Dielectric properties as function of temperature and frequency showed more than one dielectric anomaly were found at high temperatures during heating but they weakened or disappeared during cooling. Both dielectric relaxation and electrical conductivity were taken into account in point defect mechanism. The double-ionized and short-range hopping of oxygen vacancy should be mainly responsible for the dielectric anomalies and conduction behavior. Activation energy of conductivity E sub(con) is lower than half of the band gap E sub(g) obtained by UV-Vis spectroscopy, which results from emergency of oxygen vacancies. In visible light region, the ceramics show a strong absorption with band gap of about 3.57 eV.