The microstructures and dielectric properties in La2O3-doped barium strontium titanate glass-ceramics have been investigated by scanning electron microscopy (SEM) and impedance spectroscopy. SEM analysis indicated that La2O3 additive decreases the average crystallite size. Impedance spectroscopy revealed that the positions of Z '' and M '' peaks are close for undoped samples. When La2O3 concentration is 0.5 mol%, the Z '' and M '' peaks show a significant mismatch. Furthermore, these peaks separate obviously for 1.0 mol% La2O3 addition. With increasing La2O3 concentration, the contribution of the crystallite impedance becomes smaller, while the contribution of the crystal-glass interface impedance becomes larger. More interestingly, it was found that La2O3 additive increases blocking factor of the crystal-glass interface in the temperature range of 250-450 degrees C. This may be attributed to a decrease of activation energy of the crystallite and an increase of the crystal-glass interface area. (c) 2013 Elsevier Ltd. All rights reserved.