The addition of a SiO2 component to the BaO–B2O3 composition can cause the emergence of barium silicate phases and consequently achieves high coefficients of thermal expansion (11–17 ppm oC−1), whereas the introduction of an Al2O3 component to the BaO–B2O3–SiO2 composition can result in the formation of a hexacelsian phase, which can achieve a low permittivity and loss (permittivity: 7.1–7.4; loss: 5–7 × 10−4). The work may be referenced for the fabrication of LTCC materials with tailored physical properties.