Synthesis And Microwave Dielectric Properties Of NdNbO₄Ceramic System

We demonstrate the synthesis and microwave dielectric properties of theNdNbO₄dielectric ceramics. Different Nd/Nb mole ratios and CaF2additives wereused to prepare the NdNbO₄ceramics, which aimed to improve the dielectricproperties. Further, CuO was employed as sintering aid to decrease the sinteringtemperature of the system. The optimal processing parameters for preparing NdNbO₄ceramics were obtained. Moreover, the crystal structure, microscopic morphology andmicrowave dielectric properties of NdNbO₄ceramics were investigatedsystematically.Firstly, the NdNbO₄ceramics were prepared by conventional mixed oxide route.The effect of the Nd/Nb mole ratio on the sintering behaviors, phase composition,micromorphology and microwave dielectric properties were investigatedsystematically and an optimal Nd/Nb mole ratio of1.15:1was obtained. Based on thisresult, the influence of processing parameters on the dielectric properties of NdNbO₄ceramics were studied, the well-sintered NdNbO₄ceramics was obtained: calcined at900℃, re-milled for6h and sintered at1275℃.Secondly, in order to improve the microwave dielectric properties of NdNbO₄ceramics, different mass fractions of CaF2additives were doped, and the effect of theaddition of CaF2additive on the sintering behaviors, microstructure, and microwavedielectric properties of the system was investigated systematically. The resultsshowed that the phase composition, grain sizes and dielectric properties of the systemchanged with the amount of CaF2additive. These could be understood by the presenceof the second phase of CaNb2O6which existed on the grain boundaries of main phaseNdNbO₄and the presence of CaNb2O6phase affected the density of the materials, thevacancies and the order of the cations significantly.Lastly, in order to reduce the sintering temperature of NdNbO₄ceramics, CuOdoping and CuO-2.0wt%CaF2co-doping was used and the effect on the sinteringmechanism and dielectric properties of the modified ceramic system. XRD and SEMwere employed to interpret the amount of CuO additive on the microstructure andmicrowave dielectric properties.