Application of alkali metal molybdenum bronzes as Na+-ion selective sensors up to 70°C

Single crystals of the alkali metal bronzes Na0.9Mo6O17, (Li0.5Na0.5)0.9Mo6O17, Li0.9Mo6O17 and Li0.33MoO3 were tested as Na+-ion sensors. It is shown that single crystals of Na0.9Mo6O17 fabricated into electrodes by direct solid-state contact can perform as Na+-selective electrodes at temperatures from ambient to 70°C. These sensors respond rapidly and linearly to changing Na+ concentration in the range 0.1–1 M and exhibit good stability versus time and temperature. The (Li0.5Na0.5)0.9Mo6O17 crystal was insensitive to changing Na+ concentration while the Li0.9Mo6O17 and Li0.33MoO3 showed nonlinear behavior.