Effect of lithium-based glass addition on the microwave dielectric properties of Ca[(Li1/3Nb2/3)1-xTix]O3-δ ceramics for LTCC applications

The Ca[(Li1/3Nb2/3)(1-x)Ti-x]O3-delta (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 degrees C to 950 degrees C and 900 degrees C, respectively. The Ca[(Li1/3Nb2/3)(0.8)Ti-0.2]O3-delta ceramics with 5 wt% of LBS glass sintered at 950 degrees C has epsilon(r) = 30.5, Q(u)f = 14,700 GHz (f = 4.6 GHz) and tau(f) = -18 ppm/degrees C. Addition of 12 wt% of LMZBS glass in Ca[(Li1/3Nb2/3)(0.8)Ti-0.2]O3-delta ceramics sintered at 900 degrees C showed epsilon(r) = 26.2, Q(u)f = 13,000 GHz (f=4.8 GHz) and tau(f) = -21 ppm/degrees C. The tau(f) value decreased to below 10 ppm/degrees C by increasing the titanium content in the Ca[(Li1/3Nb2/3)(0.8)Ti-0.2]O3-delta ceramics. The Ca[(Li1/3Nb2/3)(0.75)Ti-0.25]O3-delta ceramics with 5 wt% of LBS and sintered at 950 degrees C/4 h has epsilon(r) = 32.8, Q(u)f = 11,500 GHz (f = 4.5 GHz) and tau(f) = -2 ppm/degrees C. The 12 wt% LMZBS glass added Ca[(Li1/3Nb2/3)(0.75)Ti-0.25]O3-delta ceramics sintered at 920 degrees C/4 h has epsilon(r) = 28.52, Q(u)f = 11,000 GHz (f = 4.8 GHz) and tau(f) = -3 ppm/degrees C. (C) 2008 Elsevier B.V. All rights reserved.