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Nowadays, low-temperature co-fired ceramic (LTCC) technology has become one of the main forms of manufacturing electronic devices. However, a majority of microwave dielectric ceramics are not suitable as LTCC materials due to their high sintering temperatures. Developing novel LTCC materials with good microwave dielectric properties is extremely urgent. In this paper, an LiF sintering aid was added to Li2Ti0.8(Co1/3Nb2/3)0.2O3 (LTCN) ceramics to explore new LTCC materials. The sintering behavior, microstructure and microwave dielectric properties of LTCN + x wt% LiF ceramics were investigated in detail. The results indicated that the addition of LiF increased the degree of disorder in the LTCN matrix, transforming it from a monoclinic to a cubic crystal system. The ceramics exhibited relatively dense and homogeneous microstructures at the sintering temperature of 950 °C as the LiF doping amount was not less than 2 wt%. By LiF doping, the quality factor (Q × f) value was significantly enhanced due to the improved microstructure. Meanwhile, the temperature coefficient of resonant frequency (τf) of LTCN ceramics was successfully regulated to the near zero value owing to the negative τf characteristic of LiF. Excellent microwave dielectric properties of dielectric constant (εr) = 19.01, Q × f = 144,890 GHz, τf = −1.52 ppm/°C were obtained when the sample doped 3 wt% LiF was sintered at 950 °C for 3 h. Furthermore, the good chemical compatibility of the LTCN-3 wt% LiF ceramic with silver electrodes suggested that the ceramic was a potential material for LTCC applications. [ABSTRACT FROM AUTHOR]

In this paper, a series of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 (0.0 ≤ x ≤ 0.4) ceramics were prepared via the conventional solid-state method. The influences of (Co 1/3 Nb 2/3)4+ complex ions on the phase composition, spectral characteristics, microstructure, and microwave dielectric properties of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 ceramics were studied systematically. XRD analysis accompanied with Rietveld refinements showed that pure Li 2 ZnTi 3 O 8 solid solution ceramics with the cubic spinel structure were obtained at x = 0.2–0.4. New Raman-active mode of about 858 cm−1 should be attributed to the vibrations of NbO 6 due to the high bond energy of Nb–O bonds, exerting a certain impact on the structure and performance of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 ceramics. XPS results indicated that Nb5+ ion donor suppressed the deoxidation process and therefore resulted in the disappearance of Ti3+ ion and oxygen vacancy. The downward trend variation in the ε r value with the increase of (Co 1/3 Nb 2/3)4+ content could be explained by the presence of "compressed" cations and "rattling" cations effect. In addition, the Q × f of the current ceramics was closely dependent on relative density, grain size, FWHM, and oxygen vacancy. Good combined microwave dielectric properties of ε r = 24.5, Q × f = 91,250 GHz, and τ f = −16.8 ppm/°C were achieved for the Li 2 Zn[Ti 0.8 (Co 1/3 Nb 2/3) 0.2 ] 3 O 8 ceramic sintered at 1120 °C. High quality factor gives evidence that the Li 2 Zn[Ti 0.8 (Co 1/3 Nb 2/3) 0.2 ] 3 O 8 ceramic is an appealing candidate for highly selective microwave devices. [ABSTRACT FROM AUTHOR]

In this study, LiF was utilized to decrease sintering temperature, improve microstructure, enhance Q × f , and regulate τ f of Li 2 Ti 0.9 (Zn 1/3 Ta 2/3) 0.1 O 3 (abbreviated as LTZT) ceramics. A complete solid solution together with a phase transition from monoclinic to cubic rock salt structure occurred. The cell volume of LTZT ceramics decreased as the LiF content increased. Relatively dense and uniform microstructures were observed for the ceramics as the LiF content was not less than 2 wt%. The dielectric constant of LTZT ceramics initially increased and then decreased with the increasing LiF content. The FWHM of the Raman band at about 808 cm−1 was closely related to the Q × f value. Notably, the samples with 3 wt% LiF exhibited the highest relative density of 97.4 % and satisfactory microwave dielectric properties of ε r = 23.14 ± 0.16, Q × f = 110,090 ± 1100 GHz, and τ f = +3.25 ± 1.45 ppm/°C when sintered at 950 °C. Good chemical compatibility with silver indicated the ceramic is a promising candidate in LTCC applications. [ABSTRACT FROM AUTHOR]