High Performance Ammonia Sensor Based on Solid Electrolyte

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The sensor output variation with the NH_3 content at 225ﾟC for the reference electrode (a) Pr_2(S0_4)_3・(NH_4) _2S0_4 and (b) Nd_2(S0_4)_3・(NH_4)_2S0_4, respectively, were measured.The operating temperature was set as the temperature where the sulfates applied in the reference electrode become anhydrous.The relation between the sensor output and the logarithm of ammonia gas pressure shows a straight line and the slope of the line exactly coincides with the slope calculated from the value obtained from the Nernst equation.If the concentration in the test gas atmosphere is exactly the same with the ammonia content in the reference electrode compartment, the sensor's output becomes zero.From the figure, the ammonia concentration in both the Pr_2(S0_4)_3・(NH_4)_2S0_4 and the Nd_2(S0_4)_3・(NH_4)_2S0_4 reference electrode compartment can be precisely estimated to be approximately 3 ppm.In conclusion, the compact NH_3 sensor composed of the NH_4^+ ion conducting solid electrolyte and the rare earth ammonium sulfate as the reference electrode was demonstrated to respond the NH_3 gas concentration exactly to the Nernst relation with continuous, rapid and reproducible responses.The outstanding feature of the sensor's quantitative NH_3 detection, contributes greatly to identifying the toxic ammonia gas leakage site as well as in situ monitoring of the ammonia content.