Development of Solid Electrolyte ECP Sensor for High Temperature Water System

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A newly designed electrochemical potential (ECP) sensor has been developed for electrochemical measurement in high temperature water systems and its thermodynamic response has been confirmed at temperatures up to 523K.The principal findings of this work are summerized as follows.1.A solid electrolyte ECP sensor was designed and fabricated. This sensor is composed of an yttria stabilized zirconia (YSZ,ZrO_2-8mol%Y_2 O_3) disk electrode with a sputter-deposited Ni・NiO composite film on the backside, an asbestos plug soaked with a neutral phosphate buffer solution as an internal solution, and an oxidized zircaloy-4 body.2.The potential of the solid electrolyte ECP sensor with respect to an Ag/AgCl (0.1kmol・m^<-3>KCl) internal refernce electrode was independent of solution pH at temperatures over the range of 473K to 523K.3.The ECP sensor had the following linear relationship with temperature in the range of 473 to 523K :E_<YSZ/NiO>=2395-5.37T/mV vs.SHE4.The long-term stability of the sensor was confirmed through the potential measuremet combined with Pt-hydrogen electrode.5.Using the solid electrolyte ECP sensor, the measurement of anodic polarization curves of SUS 304 stainless steel in a 0.5kmol・m^<-3>Na_2SO_4 solution at temperatures up to 563K has been performed. Anodic polarization curves measured with the ECP sensor coincided with those with the Ag/AgCl internal reference electrode in the temperature range from 473 to 563K.