Regulatory effects of wollastonite seeds on the crystallization process and dielectric properties of CaO-B2O3-SiO2 microcrystalline glass

Low Temperature Co-Fired Ceramic (LTCC) substrates used for microwave circuits typically must have low dielectric loss and low permittivity, as well as the ability to co-fire with metals. The dielectric properties of the microcrystalline glass materials used as the LTCC substrates are closely related to the crystallization process during sintering. This study focuses on the crystallization process of CaO-B 2 O 3 -SiO 2 microcrystalline glass. Wollastonite and pseudowollastonite seeds were used to control the degree of crystal precipitation. The phase composition and microstructure of each sample were analyzed in detail to elucidate the changes in the dielectric properties and sintering performance of the material. The addition of crystal seeds as nucleation sites promoted crystallization and led to the formation of quartz crystals. The sintered samples exhibited excellent dielectric properties: ε r  < 4 at 18 GHz, tan δ  < 0.0015, and Q  ×  f  > 12000 GHz. They have great potential as high-performance LTCC substrates.