Effect of lithium-based glass addition on the microwave dielectric properties of Ca[(Li 1/3Nb 2/3) 1− xTi x]O 3− δ ceramics for LTCC applications

Abstract

The Ca[(Li 1/3Nb 2/3) 1− x Ti x ]O 3− δ ( x = 0.2 and 0.25) (CLNT) ceramics with lithium borosilicate (LBS) and lithium magnesium zinc borosilicate (LMZBS) glasses were prepared by conventional solid state ceramic route. The effect of glass addition on the densification, microstructure and microwave dielectric properties of the CLNT ceramics was investigated. The addition of LBS and LMZBS glasses improved the densification and lowered the sintering temperature of CLNT ceramics from 1175 °C to 950 °C and 900 °C, respectively. The Ca[(Li 1/3Nb 2/3) 0.8Ti 0.2]O 3− δ ceramics with 5 wt% of LBS glass sintered at 950 °C has ɛ r = 30.5, Q u f = 14,700 GHz ( f = 4.6 GHz) and τ f = −18 ppm/°C. Addition of 12 wt% of LMZBS glass in Ca[(Li 1/3Nb 2/3) 0.8Ti 0.2]O 3− δ ceramics sintered at 900 °C showed ɛ r = 26.2, Q u f = 13,000 GHz ( f = 4.8 GHz) and τ f = −21 ppm/°C. The τ f value decreased to below 10 ppm/°C by increasing the titanium content in the Ca[(Li 1/3Nb 2/3) 0.8Ti 0.2]O 3− δ ceramics. The Ca[(Li 1/3Nb 2/3) 0.75Ti 0.25]O 3− δ ceramics with 5 wt% of LBS and sintered at 950 °C/4 h has ɛ r = 32.8, Q u f = 11,500 GHz ( f = 4.5 GHz) and τ f = −2 ppm/°C. The 12 wt% LMZBS glass added Ca[(Li 1/3Nb 2/3) 0.75Ti 0.25]O 3− δ ceramics sintered at 920 °C/4 h has ɛ r = 28.52, Q u f = 11,000 GHz ( f = 4.8 GHz) and τ f = −3 ppm/°C.