ABSTRACT
MgNb2O6 ceramics doped with (Li2O-MgO-ZnO-B2O3-SiO2) glass were synthesized by the traditional solid phase reaction route. The effects of LMZBS addition on microwave dielectric properties, grain growth, phase composition and morphology of MgNb2O6 ceramics were studied. The SEM results show dense and homogeneous microstructure with grain size of 1.72 µm. Raman spectra and XRD patterns indicate the pure phase MgNb2O6 ceramic. The experimental results show that LMZBS glass can markedly decrease the sintering temperature from 1300 °C to 925 °C. Higher density and lower porosity make ceramics have better dielectric properties. The MgNb2O6 ceramic doped with 1 wt% LMZBS glass sintered at 925 °C for 5 h, possessed excellent dielectric properties: ε r = 19.7, Q·f = 67 839 GHz, τ f = -41.01 ppm °C-1. Moreover, the favorable chemical compatibility of the MgNb2O6 ceramic with silver electrodes makes it as promising material for low temperature co-fired ceramic (LTCC) applications.
ABSTRACT
Low loss Li2NiZrO4 ceramics with rock salt structure were successfully prepared by the solid-phase reaction method. The relationship between sintering temperature, phase composition and dielectric properties of Li2NiZrO4 ceramics was reported for the first time. The grain size gradually increased and the porosity decreased with the sintering temperature increasing. When the sintering temperature exceeds 1300 °C, the grains grow abnormally and some grains begin to melt. The XRD patterns indicated the second phase ZrO2 appeared due to the volatilization of lithium. The grains grow abnormally and a second phase of ZrO2 increased the loss of Li2NiZrO4 ceramics. The samples sintered at 1300 °C possessed the best dielectric properties: ε r = 12.3, Q f = 20000 GHz, τ f = -23.4 ppm °C-1, which would make the ceramic a possible candidate for millimeter-wave applications.
