Thermal and electrical properties of copper oxide doped BiNbO4ceramics as well as its spectral characteristics and microstructure were studied in this work. According to XRD, the samples calcined at 950 C and 1100 C had the structure ofa-BiNbO4in spite of the phase transitiona/g(b)at1040 C. Thestudied composite samples had the composition of BiNb1-хCuх-yO4-d$yСuO (х=0.04) and were characterized by the graphite color and visually pronounced grain microstructure. The DSC-curves of thesamples revealed the reversible endoeffect near 900 C associated with copper (II) oxide decompositionand the thermal effects caused by the chain of reconstructive phase transitionsa/g/b’/bin BiNb1-хCuх-yO4-d. It was established that the presence of copper oxide additive in the samples increased thedensity of the ceramics, on average, by 8e10% and had a thermostatic effect on the compacted samplesmanifested in the increase in thea/g(b) phase transformation temperature by ~ 100C. The massspectrum of vapor over the BiNb1-хCuх-yO4-d$yСuO samples in vacuum has shown the ionic currents ofBiþand O2þ. The absence of Cuþions in the mass spectrum of vapor was due to low partial pressure ofcopper vapor. The comparison of the Cu2p-NEXAFS spectra of copper oxides (I) and (II) and BiNb1-хCuх-yO4-d$yСuO, synthesized at 950 C and 1100 C allowed to conclude that copper atoms were in the Cu(II)state in the studied ceramics. The impedance spectroscopy showed that an increase in the coppercontent reduced the conductivity of the samples synthesized at 950 C and increased the conductivity ofthe samples synthesized at 1100 C. A threefold increase in the copper content led to an increase in low-frequency dielectric losses by 20% in the samples synthesized at 1100 C. The growth of the capacity ofthe samples with decreasing frequency indicated the ion-migration nature of polarization.