Influence of lanthanum substitution on microstructure and impedance behavior of barium strontium titanate glass-ceramics

Abstract

Barium strontium titanate glass-ceramics with different La2O3 contents (0, 0.5, 1.0, and 1.5 mol. %) were prepared by the melt-quenching technique. The phase developments, microstructures, and impedance behavior of these glass-ceramics have been investigated as a function of La2O3 content. By the X-ray diffraction study, a gradual change with increasing La2O3 content was observed. X-ray photoelectron spectroscopy indicated that the oxygen vacancy concentration decreases with the increase of La2O3 content. Lanthanum substitution resulted in an initial increase and then a decrease in the value of dielectric constant. From impedance spectroscopy, there are two electrical responses occurring: a low frequency response, which is related to the crystal-glass interface, and a high frequency response corresponding to the crystal phase. The low frequency peak shifts to lower frequencies and the high frequency peak shifts to higher frequencies with increasing lanthanum content. Both the temperature sensitivity of impedance and the value of ac conductivity decrease with the increase of La2O3 content.