Search

Here, Ca5Mn4−xNixV6O24 (CMNVO, x = 0.00–0.08) ceramics are successfully prepared by the solid-phase reaction method, and the connection between the physical phase information, microscopic morphology, Raman spectroscopy, and microwave dielectric properties is explored. The experimental results show that Ni2+ occupies the Mn2+ sites without altering the crystal structure and is effectively solid-solvated into the lattice. The relative density reaches a maximum value of 95.9% when the temperature (Tem.) = 900°C and x = 0.06. The trend of the dielectric constant (εr) depends on the ionic polarization rate, and the quality factor (Q×f values) are correlated with the microstructure and relative density. The maximum value of 43,800 GHz is reached at Tem. = 900°C and x = 0.06, and the temperature coefficient of resonant frequency (τf values) is enhanced from −75 ppm/°C to −52 ppm/°C. The CMNVO (x = 0.06) ceramic obtains better microwave dielectric properties (εr = 11.4, Q×f = 43,800 GHz, and τf = −52 ppm/°C). This ceramic material is expected to be a candidate for low-temperature co-fired ceramic (LTCC) microwave devices. [ABSTRACT FROM AUTHOR]

The sintering behavior, microstructure, and microwave dielectric properties of Li2(Mg0.96Ni0.04)SiO4 ceramics with different amounts of LBS and LBSCA glass were studied. This experiment is based on the traditional solid-state reaction method. In this work, the microstructure of the composite ceramics with different kinds of glass was analyzed by SEM. Excellent microwave dielectric properties of the composite ceramics were obtained with sintering at 900°C: ε r = 5.49, Q × f = 18,448 GHz at 16 GHz, τ f = −15.3 ppm/°C with 4 wt.% LBS glass, ε r = 5.58, Q × f = 20,248 GHz at 16 GHz, τ f = −15.2 ppm/°C with 2 wt.% LBSCA glass. The addition of CaO and Al2O3 helped to improve the efficiency of sintering in the Li2(Mg0.96Ni0.04)SiO4 ceramic. [ABSTRACT FROM AUTHOR]

In this paper, the microstructures, resistivity as well as temperature coefficient of resistance (TCR) of La0.5Sr0.5Co1−xVxO3 (x = 0.00–0.10) ceramics were studied. These ceramic samples were prepared through conventional solid-state reaction method. Results showed that the substitution of Co ions with V ions improved the densification level of ceramic samples and changed their resistive characteristics accordingly. A uniform microstructure of La0.5Sr0.5 Co1−xVxO3 ceramic was realized at x = 0.05 when sintered at 1100°C. The resistivity of ceramics increased slightly as the V content varied in the range of 0.00–0.10. The TCR value of all tested samples was maintained between +1304.35 ppm/°C and +2958.26 ppm/°C. A low resistivity value of 0.38 mΩ cm and the minimum TCR value of +1304.35 ppm/°C were achieved as x = 0.05 in La0.5Sr0.5Co1−xVxO3. It was found that the substitution of Co ions with V ions facilitated lowering the TCR value without changing the resistivity too much. Thus, these ceramics are promising materials for conductive oxide used in thick-film resistors. [ABSTRACT FROM AUTHOR]

The microstructure, sintering behavior, and microwave dielectric properties of LiZn1−xCoxPO4 (x = 0.00-0.10) ceramics were investigated. All these materials were synthesized by the traditional solid-state reaction method. Component and microstructure of the ceramics were verified by x-ray diffraction (XRD) patterns and scanning electron microscopy (SEM), respectively. The substitution of Co2+-ion to Zn2+-ion would improve the densification level of composite ceramics, and the microwave dielectric properties would be changed accordingly. An excellent microwave dielectric property of LiZn1−xCoxPO4 (x = 0.00-0.10) was achieved when x = 0.07 (ɛr = 5.43, Q × f = 35,446 GHz at 15 GHz, τf = − 77.4 ppm/°C). In order to achieve reliable thermal stability, Pb1.5Nb2O6.5 was used to adjust its τf value. The LiZn0.93Co0.07PO4 ceramics with 6 vol.% Pb1.5Nb2O6.5 sintered at 750°C for 4 h shows a near-zero τf value of − 4.4 ppm/°C, ɛr = 6.09, Q × f = 14,305 GHz (at 15 GHz), and there was no chemical reaction between Pb1.5Nb2O6.5 and LiZn0.93Co0.07PO4. The composite ceramics are promising materials for millimeter-wave device applications in the field of low temperature co-fired ceramics. [ABSTRACT FROM AUTHOR]