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Low temperature co-fired ceramics (LTCCs) technology plays an important role in modern wireless communication. Zn 3- x Co x B 2 O 6 (x = 0–0.25) low temperature fired ceramics were synthesized via traditional solid-state reaction method. Influences of Co2+ substitution on crystal phase composition, grain size, grain morphology, microwave dielectric properties, bond energy, and bond valence were investigated in detail. X-ray diffraction analysis indicated that the major phase of the ceramics was monoclinic Zn 3 (BO 3) 2. Solid solution was formed with Co2+ substituted for Zn2+ because no individual phase that contained Co was observed. An increase in the amount of Co2+ substitution changed average grain sizes, and regrowth of grains were observed with Co2+ substitution. Appropriate amount of Co2+ substitution improved densification. With changes in Co2+ substitution, bond energy of major phase and average bond valence of B–O were positively correlated to temperature coefficient of resonant frequency. The Zn 2.927 Co 0.075 B 2 O 6 ceramic sintered at 875 °C for 4 h exhibited excellent microwave properties with ε r = 6.79, Q × f = 140,402 GHz, and τ f = −87.42 ppm/°C. This ceramic is regarded as candidate for LTCC applications. [ABSTRACT FROM AUTHOR]

In this work, Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics (x = 0–0.4) added with 3 wt% Li 2 O–B 2 O 3 –Bi 2 O 3 –SiO 2 (LBBS) glass were synthesised using the solid-state reaction method. The effects of substituting Co2+ for Mg2+in Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics on crystal structure, microstructure, densification, crystallisation and microwave dielectric properties were investigated. X-ray diffraction patterns showed that monoclinic Li 2 MgSiO 4 , monoclinic Li 2 ZnSiO 4 and orthorhombic Li 2 CoSiO 4 formed finite solid solution in Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics. Clear grain boundaries were observed via scanning electron microscopy. The substitution of Co2+ for Mg2+ increased grain size, densification, crystallinity degree and dielectric constant; it also reduced the dielectric loss of the ceramics to a certain extent. The absolute values of τ f were positively related to the crystallinity degree. Li 2 Mg 0.55 Co 0.05 Zn 0.4 SiO 4 ceramic added with 3 wt% LBBS and sintered at 900 °C exhibited considerable microwave dielectric properties of ε r = 5.8, Q × f = 47,518 GHz and τ f = −74.8 ppm/°C. Therefore, the ceramic is considered a candidate low-temperature co-fired ceramic material for substrate and filter applications. [ABSTRACT FROM AUTHOR]

The crystal structure and microwave dielectric properties of Zn 3-x Cu x (BO 3) 2 (x = 0–0.12) ceramics prepared via a traditional solid-state reaction method were investigated by means of X-ray diffraction (XRD) utilizing the Rietveld refinement, complex chemical bond theory, and Raman spectroscopy. XRD showed that all samples were single phase. The samples maintained a low permittivity, even at higher Cu2+ contents, which is conducive to the shortening of signal delay time, and intimately related to the average bond ionicity and Raman shift. Moreover, proper Cu2+ substitution greatly reduced the dielectric loss associated with the lattice energy. Cu2+ entering the lattice optimized the temperature coefficient of resonance frequency (τ f) values and improved the temperature stability of samples by affecting the bond energy. Optimal microwave dielectric properties were: ε r = 6.64, Q × f = 160,887 GHz, τ f = −42.76 ppm/°C for Zn 2.96 Cu 0.04 (BO 3) 2 ceramics sintered at 850 °C for 3 h, which exhibited good chemical compatibility with silver and are therefore good candidate materials for Low temperature co-fired ceramic applications. [ABSTRACT FROM AUTHOR]