Crystal structure and microwave dielectric properties of NaPb2B2V3O12(B = Mg, Zn) ceramics

Two low temperature sintered NaPb2B2V3O12 (B = Mg, Zn) ceramics with garnet structure were synthesized through conventional solid state reaction route and their crystal structure and microwave dielectric properties were investigated for the first time. Rietveld refinements of XRD patterns show both the compounds belong to cubic symmetry with space group Ia-3d. Observed number of Raman bands and group theoretical predictions also confirm cubic symmetry with space group Ia-3d for both NPMVO and NPZVO. At the optimum sintering temperature of 725 degrees C NPMVO has a relative permittivity of 20.6 +/- 0.2, unloaded quality factor (Q(u)xf) of 22,800 +/- 1500 GHz (f = 7.7 GHz) and temperature coefficient of resonant frequency +25.1 +/- 1 ppm/degrees C while NPZVO has relative permittivity of 22.4 +/- 0.2, Q(u)xf of 7900 1500 GHz (f = 7.4 GHz) and near zero temperature coefficient of resonant frequency of -6 +/- 1 ppm/degrees C at 650 degrees C. The relative permittivity of the compounds is inversely related to the corresponding Raman shifts.