Phase composition, crystal structure, complex chemical bond theory and microwave dielectric properties of high-Q materials in a (Nd1-xYx)NbO4 system

In this paper, (Nd1-xYx)NbO4 ceramics are prepared via a conventional solid-state reaction method and their microwave dielectric properties have been reported for the first time. The Rietveld refinement was used to investigate the crystal structure of (Nd1-xYx)NbO4 ceramics. Based on the refined results, the NdNbO4 ceramics have a monoclinic fergusonite structure (I2/a (15) space group, Z = 4). The XRD patterns present a single monoclinic phase of NdNbO4 in the range of x = 0.02 to 0.1, with a further increase in the substitution content of Y3+ ions, few impurity phases are formed. In order to evaluate the correlations between complex chemical bond theory and microwave dielectric properties, the ionic polarization, lattice energy and bond energy were calculated using the refined lattice parameters and bond length. The effects of substituting Y3+ ions for Nd3+ ions on the microwave dielectric properties of the (Nd1-xYx)NbO4 ceramics were also discussed. The increase in the dielectric constant epsilon(r) is due to increasing the corrected theoretical dielectric constant epsilon(rc). For high relative density samples, the Q x f values and tau(f) values are really dependent upon the calculated lattice energy and bond energy. High-quality factor microwave dielectric materials can be obtained with x = 0.08 in the (Nd1-xYx)NbO4 system, and show excellent dielectric properties of tau(r) = 19.87, Q x f = 81 100 GHz and tau(f) = -18.84 ppm degrees C-1.