The effects of B2O3 addition on the microwave dielectric properties and the microstructures of (1 - x)LaAlO3-xSrTiO(3) ceramics prepared by conventional solid-state routes have been investigated. Doping with 0.25 wt.% B2O3 can effectively promote the densification and the microwave dielectric properties of (1 - x)LaAlO3 xSrTiO(3) ceramics. It is found that LaAlO3-SrTiO3 ceramics can be sintered at 1400degreesC due to the liquid phase effect of a B2O3 addition observed by scanning electronic microscopy (SEM). The dielectric constant as well as the Q x f value decreases with increasing B2O3 content. At 1460degreesC, 0.46LaAlO(3)-0.54SrTiO(3) ceramics with 0.25 wt.% B2O3 addition possesses a dielectric constant (epsilon(r)) of 35, a Q x f value of 38,000 (at 7 GHz) and a temperature coefficients of resonant frequency (tau(f)) of -1 ppm/degreesC. (C) 2002 Elsevier Science Ltd. All rights reserved.