Synthesis and characterization of Na5M(MoO4)4 (M = Y, Yb) microwave ceramics for ULTCC applications

Na5Y(MoO4)(4) and Na5Yb(MoO4)(4) ceramics are prepared by solid state ceramic route and structural characterization has been done using powder X-ray diffraction and Laser Raman spectroscopy techniques. The presence of MoO42- units in the crystal structure is confirmed from Raman spectra. The scanning electron micrographs of the sintered ceramic samples show dense microstructure. Na5Y(MoO4)(4) ceramic exhibited a maximum sintered density of 3.6 g/cm(3) at 600 degrees C with a dielectric constant of 7.8, quality factor (Q x f) of 56,800 GHz, and temperature coefficient of resonant frequency (tau(f)) of -83 ppm/degrees C, whereas Na5Yb(MoO4)(4) ceramic showed a maximum sintered density of 3.9 g/cm(3) at 570 degrees C with a dielectric constant of 6.9, quality factor (Q x f) of 43,400 GHz, and temperature coefficient of resonant frequency (T-f) of -68 ppm/degrees C. Powder X-ray diffraction and energy dispersive X-ray spectroscopic analyses of the co-fired samples confirm good chemical compatibility with aluminium electrode for Na5Yb(MoO4)(4) ceramic and hence is a suitable candidate material for ULTCC applications.