BiNbO4 ceramic powders were prepared using the sol-gel method. The fine particles were pressed into cylinders and, then, they were treated at temperatures between 500 and 1150 degrees C. The structure was studied by X-ray diffraction and Raman spectroscopy and the morphology was observed by scanning electron microscopy. The measurements of the complex permittivity were made in a resonant cavity operating at 2.7 GHz, using the small perturbation method. The reversible phase transformation between beta-BiNbO4 and alpha-BiNbO4 was observed. The density, dielectric constant (epsilon') and the dielectric loss (tg delta) of the prepared powders increase with the sintering temperature, and the sample treated at 1150 degrees C shows the highest epsilon' and the highest Q x f. (C) 2016 Elsevier Ltd. All rights reserved.