Chemical stability and dielectric properties of RO-La2O3-B2O3 (R = Ca, Mg, Zn)-based ceramics

New lanthanum borate (La₂O₃-B₂O₃) glasses modified with divalent oxides, such as CaO, MgO and ZnO were investigated as potential low temperature dielectrics by understanding compositional dependence of dielectric properties and chemical leaching resistance. Firing behavior, such as densification and crystallization, depended strongly on the glass composition and is found to influence the resultant dielectric performance. Specifically, the dielectric composition of 20ZnO-20La₂O₃-60B₂O₃ glass with 40 wt% Al₂O₃ as a filler showed distinct enhancements of dielectric properties, i.e., k ∼ 8.3 and Q ∼ 1091 at the resonant frequency of 17.1 GHz, as a result of 850 °C firing. The result was believed related to earlier densification and unexpected evolvements of ZnAl₂O₄ and La(BO₂)₃ phases during firing. The Mg-containing glass sample was most stable in strong acid solutions and did not show any significant changes in microstructure even after 300 min exposure. The Ca-containing glass sample was not regarded as a promising candidate for low temperature dielectrics from the observed low quality factor and weak chemical durability.