Mixed-potential type NH3 sensor based on TiO2 sensing electrode with a phase transformation effect

Mixed-potential type NH3 sensors were fabricated using La10Si5.5Al0.5O27 (LSAO) consisting of a porous layer and a dense layer as solid electrolyte and TiO2 as the sensing electrode. The effect of a LSAO porous layer and TiO2 phase transformation on sensor performances was investigated. The porous layer of LSAO electrolyte obviously enhanced sensor performance. Compared with the sensor without a LSAO porous layer, the sensor with LSAO porous layer exhibited larger responding potential values and higher sensitivity due to the enhanced three phase interface length. Anatase-TiO2 (a-TiO2) based sensor exhibited better sensing performance than rutile-TiO2 (r-TiO2) based sensor at the examined temperature range. A-TiO2 transformation toward r-TiO2 resulted in, poor sensing,performances of the sensor. The best sensing characteristics were achieved for the NH3 sensor with a-TiO2 sensing electrode calcined at 900 degrees C for 3 h. The potential values of the sensor response to NH3 linearly depended on the logarithm of NH3 concentrations at 450-600 degrees C and the sensitivity reached 169.7 mV/decade in the range of 50-400 ppm at 500 degrees C. At the same time, the sensor exhibited well anti-interference capability to H-2, NO, CH4 and CO2, but a little cross-sensitivity toward NO2 was observed. High temperature treatment (>900 degrees C) caused a-TiO2 transformation into r-TiO2 and V2O5 additions were conducive to TiO2 phase transformation. (C) 2016 Elsevier B.V. All rights reserved.