BaCu(B2O5) (BCB) ceramic powder was used to decrease the sintering temperatures of BaSm2Ti4O12 (BST) and BaNd2Ti5O14 (BNT) ceramics. The sintering temperature of the BST and BNT ceramics was reduced from approximately 1350 degrees C to 850 degrees C by the addition of BCB. The bulk density of the specimens increased and reached the saturated value with increasing BCB content. The variation of the dielectric constant (epsilon(r)) was similar to that of the bulk density and, thus, the relative density plays an important role in determining the epsilon(r) value of the specimens. The Q-value initially increased with the addition of BCB but decreased considerably when a large amount of BCB was added because of the presence of the liquid phase. Good microwave dielectric properties of Qxf = 4500 GHz, epsilon(r) = 60 and tau(f) = -30 ppm/degrees C were obtained for the 16.0 mol% BCB-added BST ceramics sintered at 875 degrees C for 2 h. (C) 2006 Elsevier Ltd. All rights reserved.