The effects of B2O3 addition on the sintering behavior and the dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 (BST) ceramics were investigated. The dielectric and ferroelectric properties of a BST sample with 0.5 wt% B2O3 sintered at <1150 degrees C were as good as those of undoped BST sintered at 1350 degrees C, and the dielectric loss was better. When >1.0 wt% B2O3 was added to BST, the overdoped B2O3 did not form a liquid phase or volatilize; it remained in the samples and formed a secondary phase that lowered the sintering behavior and the dielectric acid ferroelectric properties of the BST.