A LAB glass with a composition of 10 mol% La2O3 + 10 mol% Al2O3 + 80% B2O3 made into a composite with 30-50% Al2O3 filler was prepared and investigated. Processing optimization and several engineering properties used for microwave substrates are reported, including densification, interaction with Ag electrodes, dielectric properties as a function of frequency, acid dissolution and microstructure. The glass ceramic composite, i.e. L30A, without lead and alkali, can be densified by two-step sintering to a density better than 99% with minimal glass residue. The densified composite does not react with Ag up to 950 degrees C in I h, and does not dissolve in an acid solution (pH=3.5) in 2 h. The dielectric constant and loss are in the range of 5.6-5.9 and 1.4 x 10(-3)-5.5 x 10(-3), respectively. The coefficient of thermal expansion (CTE) and thermal conductivity of the composite are reported.

Keywords: LAB; glass-ceramics; composite; microwave; dielectric; acid dissolution; CTE; thermal conductivity