Effect of composition of BaO.(R2O3)(y).(TiO2)(z).0.06(2Bi(2)O(3).3TiO(2)) materials, R = Nd(1-x)Sm(x),BRT, on the materials characteristics and microwave dielectric properties of the samples was systematically examined. The Ti/Ba ratio (z value) shows the most significant effect on the microwave dielectric properties of the materials. The Q x f-value is small for z less than or equal to 3.82 materials, and showing maximum value for z = 4.32 samples, then decrease for z = 4.52 composition, which is possibly due to the presence of secondary phase for Z = 3.82 and 4.52 materials. Diffusion couple experiments shows that the interaction diffusion zone between glass and BRT ceramic is not pronounced, so that Ba-B-Si glass and BRT could be a good low temperature co-firable ceramic system is inferable. (C) 2002 Elsevier Science B.V. All rights reserved.