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Pengshen Wu,Cuijin Pei,Miao Chen,Xu Gao,Weihong Liu,Guoguang Yao,Jin Liu 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6
By a reaction-sintering approach Li3Mg2SbO5F2 oxyfluorides ceramics were prepared. The sinterability, microstructure,phase transition along with microwave dielectric performances of present ceramics were researched. A gradual phase transitionfrom cubic to orthorhombic in Li3Mg2SbO5F2 ceramics sintered above 825 °C was identified by XRD refinement analysis. The microwave dielectric performances of present ceramics were closely correlated with its phase transition process andmicrostructure. Typically, optimal microwave dielectric performances (εr ~ 8.1, τf ~ –54.0 ppm/°C, Q × f ~ 68,500 GHz (under9.2 GHz)) were achieved for 825 °C-sintered Li3Mg2SbO5F2 ceramics. Moreover, a cylindrical dielectric resonator antennafabricated from Li3Mg2SbO5F2 ceramics exhibited a maximum return loss (S11) of –30.3 dB, a maximum gain of 5.3 dB andVSWR of 1.1 at the center frequency of 11.6 GHz, and impedance bandwidth of 300 MHz (at –10 dB), respectively.
Effects of V2O5 on sinterability and microwave dielectric properties of NaCa4V5O17 ceramics
Guoguang Yao,Yang Li,Jingjing Tan,Cuijin Pei,Yan Zhang,Jia Chen 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3
The NaCa4V5O17 ceramics owing low sintering temperature had been prepared via conventional solid state reaction methodusing V2O5 as vanadium source. The sinterability, microwave dielectric characterisations and compatibility with Ag wereinvestigated. Pure phase NaCa4V5O17 with triclinic structure was confirmed by Rietveld refinement and Raman spectrum. Thepermittivity (εr) and quality factor (Qxf) values mainly depended on the relative density, whereas the temperature coefficientof resonant frequency (τf) value was closely connected with the tetrahedral distortion of V(1)O4. The NaCa4V5O17 ceramicssintered at 800 oС owned high densification and moderate microwave dielectric performances under 10.7 GHz: εr = 9.5, Q×f= 34,200 GHz, τf = -90.0 ppm/oС, but poor chemical compatibility with Ag paste.
Wei Jin,Jingjing Tan,Jiaxin Yan,Yao Tao,Ningning Yao,Xiaomeng Ruan,Cuijin Pei 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.6
The normative solid-state reaction process was adopted to prepare Li3Mg4NbO8 ceramics with LiF addition. We investigatedthe impacts of LiF additive on the crystal structure, sinterabillity as well as dielectric performance at microwave region of theLi3Mg4NbO8-basic ceramics. XRD analysis confirmed that the addition of LiF to Li3Mg4NbO8 lead to the formation of newphase Li4Mg4NbO8F with cubic rock salt structure. The densified temperature of Li3Mg4NbO8-basic ceramics could beeffectively reduced from 1150 oC to 900 oC with LiF addition. Both the permitivity (εr) and quality factor (Qf) of presentceramics were is closely correlated with the bulk density and cell volume. The 900 oC-sintered Li3Mg4NbO8-basic ceramicsowned excellent chemical compatibility with silver and optimized microwave dielectric performance (εr ~13. 4, Qf ~ 32,400GHz at 9.4 GHz, and temperature coefficient of resonant frequency (τf) ~ -43.0 ppm/℃).