Copper concentration effect in the dielectric properties of BiNbO 4 for RF applications

In this paper, the structural and dielectric properties BiNbO4 as a function of cooper addition level and the radio frequency was investigated. The BiNbO4 ceramics, were prepared by using the solid-state reaction method with the addition of 3, 5, and 10 wt.% of CuO. The analysis by X-ray diffraction (XRD) using the Rietveld refinement confirmed the formation of single-phase compound with a orthorhombic crystal structure (a = 5.6792 angstrom, b = 11.7081 angstrom and c = 4.9823 angstrom; alpha = beta = gamma = 90 degrees) for the calcined powders. Micrographs obtained by scanning electron microscope shows the distribution of grains and the behavior of addition of CuO on the sample surface. In the measurements of the dielectric properties of BiNbO4 at room temperature, by complex impedance spectroscopy technique, showed that the largest values of dielectric permittivity (epsilon(r)') at frequency 10 kHz, were found for the samples: BNO3Cu (3 wt.% CuO), BNO5Cu (5 wt.% CuO) and BNO10Cu (10 wt.% CuO) with values epsilon(r)' = 87.15, 88.63 and 140.73, respectively. The values of the dielectric loss (Tan delta) for the samples: BNO3Cu, BNO5Cu and BNO10Cu were around 10 (2), with values of 1.27 x 10 (2), 1.81 x 10 (2), and 3.61 x 10 (2), respectively at 10 MHz. The samples were investigated for possible applications in radio frequency devices like ceramic capacitors. (C) 2012 Elsevier B.V. All rights reserved.