Development of Ag and Ag alloys-precipitated Ag2O-TeO2 glass and Ag2O-TeO2 glass/stainless steel reference electrodes for pH sensors

Abstract

An Ag/AgCl reference electrode that is built into commercially available pH electrodes leaks its internal KCl solution via a liquid junction. This leakage is disadvantageous because the test solution is contaminated by a trace amount of the KCl solution. The applicability of Ag2O-TeO2 glasses to reference electrodes for pH sensors was investigated in this study. The effects of the Ag2O content and heat treatment on the pH sensitivity of these glasses and the pH sensitivity of the Ag2O-TeO2 glass/stainless steel electrodes were examined. The pH sensitivity of Ag2O-TeO2 glasses increased as the Ag2O content increased, but it was less than 40 % and was the lowest among the glasses that have been investigated to date. The heat-treated 25Ag2O･75TeO2 glass and 25Ag2O･75TeO2 glass/stainless steel electrodes precipitated cubic Ag and hexagonal Ag and showed relatively low pH sensitivities of 26 % and 5 %, respectively. Thus, the hexagonal Ag and Ag alloys-precipitated samples were considered candidate reference electrodes for pH sensors.