In-situ Synthesis of an Auxiliary Electrode of Solid Electrochemical Sulfur Sensor by CaAl4O7 Coating

A novel auxiliary electrode CaAl 4 O 7 +Al 2 O 3 +CaS used for solid electrochemical sulfur sensor, was synthesized by the in-situ reaction of CaAl 4 O 7 coating on the surface of the ZrO 2 (MgO) electrolyte tube by: [ ] . The CaAl 4 O 7 coating was synthesized using aluminum nitrate solution and calcium hydroxide solution as raw materials and then was fabricated on the surface of the ZrO 2 (MgO) electrolyte tube using solid sintering technology at 1500 °C. The microstructure of the coating was dense and well combined with the ZrO 2 (MgO) electrolyte. The solid electrochemical sulfur sensor o was assembled and tested in the carbon-saturated molten iron at 1500 °C. The results showed that the sensor had a good stability and accuracy, and the CaAl 4 O 7 coating was converted to CaAl 4 O 7 +Al 2 O 3 +CaS when the sulfur sensor was inserted into the molten iron. The phase composition and microstructure of the synthetized auxiliary electrode were investigated after the sulfur sensor was tested, indicating that the auxiliary electrode coating with a thickness of 40-50 μm w s synth tiz d. The empirical formula of the sulfur sensor was obtained as follows: