Microwave dielectric properties of Ca0.7Nd0.2TiO3 ceramic-filled CaO-B2O3-SiO2 glass for LTCC applications

The effects of the Ca0.7Nd0.2TiO3 ceramic addition on the crystallization, densification, and dielectric properties of CaO-B2O3-SiO2-(Al2O3) glass (C1: CaO-B2O3-SiO2 glass and C1A03: CaO-B2O3-SiO2-Al2O3 glass) for low-temperature co-fired ceramic (LTCC) applications are investigated. The cristobalite phase crystallized from C1 glass was inhibited by adding Al2O3. During sintering, Ca0.7Nd0.2TiO3 ceramic reacted with CaO-B2O3-SiO2-(Al2O3) glass to form the sphene (CaTiSiO5) phase. The amount of sphene phase increases with increasing sintering temperature. By adding 50-60 wt% C1 or C1A03 glass, Ca0.7Nd0.2TiO3 can be densified at 850-900 degrees C. The relative dielectric constants for Ca0.7Nd0.2TiO3 added with C1 and C1A03 glasses were all 20-23. Ca0.7Nd0.2TiO3 added with C1 glass exhibited a lower dielectric constant than C1A03 glass due to cristobalite phase formation. For Ca0.7Nd0.2TiO3 ceramics added with 50 wt% glass, the variation in Q x f value presented the same trend as the sphene formation amount variation. The best Q x f value of 2380 GHz was achieved for Ca0.7Nd0.2TiO3 ceramics added with 50 wt% C1A03 glass sintered at 900 degrees C due to the dense structure and greater amount of sphene. Ca0.7Nd0.2TiO3 ceramics added with 50 wt% C1A03 glass sintered at 900 degrees C exhibited a dielectric constant of 22.8 and Q x f value of 2380 GHz, which are suitable for microwave LTCC applications.