Chromium niobate (CrNbO4), molybdenum niobate (Mo3Nb2O14), titanium niobate (TiNb2O7), and binary oxide based on Nb2O5 and WO3 were synthesized by low-temperature underwater plasma. The electrode materials (Nb, Mo, Cr, Ti, and W) were used as precursors. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG) analysis, and impedance analysis were used to characterize the obtained materials. The results of XRD showed that in the case of combining electrodes from niobium and molybdenum and chromium and titanium, niobates are formed, and in the niobium-tungsten pair, a mixture of oxides is formed. The results of dielectric measurements showed that the obtained materials have high dielectric constants (εr > 10–60 at f > 1 kHz). Thermal analysis data allowed us to propose a mechanism for the formation of niobates in underwater plasma conditions.
