Hongwei Yang,Fang Xu,Yulong Liao,Yong Ren,Guixiang Liu,Yan Yang,Xueying Wang,Bo Dai
In this work, we prepared a type of LiZnTiCu ferrite with a large grain size and enhanced magnetic properties at ∼900 °C by substituting Cu 2+ ions and doping LBSCA glass. Rietveld refinement of XRD patterns indicates that the Fe 3+ ions in B sites are partially replaced by the Cu 2+ ions, which causes the monotone increase of lattice constant . SEM results show that the interaction of CuO nanoparticles and LBSCA glass causes two changes in the grain growth of the LiZnTiCu ferrites. The grain growth is suppressed when the amount of CuO nanoparticles is less than a threshold value (x = 0.05 for 900 °C; x = 0.20 for 875 °C). However, when enough CuO nanoparticles are added, the ferrites possess a large and compact microstructure. The variation of magnetic hysteresis ( M - H ) loops confirms that M s follows the Néel's collinear spinel model with the increasing number of CuO nanoparticles (x ≤ 0.25). Finally, a type of LiZnTiCu ferrite (x = 0.15) with uniform large grains (average size >10 μm) and good magnetic parameters (4π M s = 3457.59 G, H c = 224.4 A/m and B s = 236.4 mT) is obtained at ∼900 °C.
In this study, low-temperature fired CaMg 1− x Li 2 x Si 2 O 6 microwave dielectric ceramics were prepared via the traditional solid-state reaction method. In this process, 0.4 wt% Li 2 CO 3 -B 2 O 3 -SiO 2 -CaCO 3 -Al 2 O 3 (LBSCA) glass was added as a sintering aid. The results showed that ceramics consisted of CaMgSi 2 O 6 as the main phase. The second phases were CaSiO 3 always existing and Li 2 SiO 3 occurring at substitution content x > 0.05. Li + substitution effectively lowered sintering temperature due to 0.4 wt% LBSCA and contributed to grain densification, and the most homogeneous morphology could be observed at x = 0.05. The effects of relative density, the second phase, and ionic polarizability on dielectric constant (ε r ) were investigated. The quality factor ( Q × f ) varied with packing fraction that concerned the second phase. Moreover, the temperature coefficient of the resonant frequency (τ f ) was influenced by MgO 6 octahedral distortion and bond valence. Excellent dielectric properties of the CaMg 1− x Li 2 x Si 2 O 6 ceramic was exhibited at x = 0.05 with ε r = 7.44, Q × f = 41,017 GHz ( f = 15.1638 GHz), and τ f = −59.3 ppm/°C when sintered at 900 °C. It had a good application prospect in the field of low-temperature co-fired ceramic (LTCC) substrate and devices.
Fangyi Huang,Jiaqing Du,Xiaoli Tang,Qin Zhang,Xingyu Huo,Yuanxun Li,Xian Jian,Hua Su
Ba 0.8 Sr 0.2 CuSi 2 O 6 ceramics have a low dielectric constant, which is useful for low-latency 5G communication. To enable the preparation of Ba 0.8 Sr 0.2 CuSi 2 O 6 low-temperature co-fired ceramic (LTCC) materials, LBSCA and LBBS were used in this paper to reduce the sintering temperature of Ba 0.8 Sr 0.2 CuSi 2 O 6 . The effects of LBSCA and LBBS on the phase composition, densification, microscopic morphology, and vibrational characteristics of the ceramics were investigated by X-ray diffraction, scanning electron microscopy, density measurements, and Raman spectroscopy , and the causal factors influencing the microwave dielectric properties with the addition of glass were analyzed. It was found that 0.4 wt% LBSCA glass and 1 wt% LBBS glass reduced the sintering temperature to 925 °C, and these prepared ceramics had excellent microwave dielectric properties. The ceramic prepared with 0.4 wt% LBSCA glass had an ε r value of 7.672, Q × f value of 37193 GHz, and τ f value of −14.93 ppm/°C, while the ceramic prepared with 1 wt% LBBS glass had an ε r value of 7.512, Q × f value of 32136 GHz, and τ f value of −13.92 ppm/°C. The phase composition of the ceramics did not significantly change, indicating that neither glass reacted with the ceramics. The ε r value was affected by both density and Raman shift, the trend in the Q × f values was consistent with the density, and the τ f value decreased with increasing glass content, which was attributed to the liquid phase generated by the glass in the ceramic. In addition, co-firing these glass-doped ceramics with Ag at a low temperature resulted in good chemical compatibility. Combined with the near-zero τ f , these results demonstrate the excellent promise of these two ceramics as alternative materials for LTCC microwave devices and their application in 5G communication.
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