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

Abstract

The effects of the Ca 0.7 Nd 0.2 TiO 3 ceramic addition on the crystallization, densification, and dielectric properties of CaO-B 2 O 3 -SiO 2 -(Al 2 O 3 ) glass (C1: CaO-B 2 O 3 -SiO 2 glass and C1A03: CaO-B 2 O 3 -SiO 2 -Al 2 O 3 glass) for low-temperature co-fired ceramic (LTCC) applications are investigated. The cristobalite phase crystallized from C1 glass was inhibited by adding Al 2 O 3 . During sintering, Ca 0.7 Nd 0.2 TiO 3 ceramic reacted with CaO-B 2 O 3 -SiO 2 -(Al 2 O 3 ) glass to form the sphene (CaTiSiO 5 ) phase. The amount of sphene phase increases with increasing sintering temperature. By adding 50–60 wt% C1 or C1A03 glass, Ca 0.7 Nd 0.2 TiO 3 can be densified at 850–900 °C. The relative dielectric constants for Ca 0.7 Nd 0.2 TiO 3 added with C1 and C1A03 glasses were all 20–23. Ca 0.7 Nd 0.2 TiO 3 added with C1 glass exhibited a lower dielectric constant than C1A03 glass due to cristobalite phase formation. For Ca 0.7 Nd 0.2 TiO 3 ceramics added with 50 wt% glass, the variation in Q × f value presented the same trend as the sphene formation amount variation. The best Q × f value of 2380 GHz was achieved for Ca 0.7 Nd 0.2 TiO 3 ceramics added with 50 wt% C1A03 glass sintered at 900 °C due to the dense structure and greater amount of sphene. Ca 0.7 Nd 0.2 TiO 3 ceramics added with 50 wt% C1A03 glass sintered at 900 °C exhibited a dielectric constant of 22.8 and Q × f value of 2380 GHz, which are suitable for microwave LTCC applications.