Control of microwave dielectric properties of Ca Ti O 3 -basedhigh-permittivity ceramics using additives

The effects of Li 2 O - Bi 2 O 3 - Ti O 2 (LBT) additions on the microwave dielectric properties of high-permittivity Ca O - Sm 2 O 3 - Li 2 O - Ti O 2 (CSLT) ceramics have been investigated. Addition of LBT up to 10 wt % simultaneously reduced the sintering temperature and improved the density of the sintered CSLT ceramics. Scanning electron microscope (SEM) analysis showed a secondary phase when up to 10 wt % of LBT was added to CSLT, which disappeared at higher sintering temperatures. However, x-ray diffraction (XRD) analysis revealed that all the compositions had a distorted perovskite structure. By varying the amounts of LBT additions within 0.5 - 10 wt % of the main component and the sintering temperature ( 1200 - 1400 ° C ) , a wide range of dielectric properties with permittivity in the range of 92-113, Q f > 3000 GHz , and TC f = ± 20 ppm ∕ ° C were obtained. For example, with 1.0 wt % LBT additions sintered at 1400 ° C , ε r = 94.02 , Q f = 5970 GHz , and TC f = 6.8 ppm ∕ ° C ; with 5.0 wt % LBT additions sintered at 1350 ° C , ε r = 101.91 , Q f = 5050 GHz , and TC f = 0.4 ppm ∕ ° C ; with 10.0 wt % LBT additions sintered at 1250 ° C , ε r = 112.12 , Q f = 3560 GHz , and TC f = 1.0 ppm ∕ ° C . These combinations of advantages make LBT a very useful additive in developing a range of dielectric characteristics in Ca O - Ln 2 O 3 - Li 2 O - Ti O 2 group of microwave dielectric ceramics.