Gallium and titanium containing niobates with the compositions Ni 4 -x Ga 2/3x Nb 2 O 9 and Ni 4 -x Ti x/2 Nb 2 O 9 have been synthesized and their physicochemical properties have been studied. Their unit cell parameters have been determined by X ray diffraction and their electrical conductivity has been mea sured as a function of temperature. According to thermomechanical analysis data, the niobates undergo no phase transitions. Some of the solid solutions have been used to fabricate Ni selective electrodes, which have been tested in ion selective measurements. In a number of cases, satisfactory results have been obtained.