KCl-leakage-free reference electrode based on Ag2O–TeO2 glass and Ti

The primary objective of this study was to develop KCl-leakage-free reference electrodes for biomedical, clinical, and food applications, as well as for use in the semiconductor industry. Accordingly, we developed new reference electrodes based on Ag 2 O–TeO 2 glass and Ti, employing Ag 2 O–TeO 2 glass/Ti and Ti/ Ag 2 O–TeO 2 glass/stainless steel (SUS) configurations in particular. The investigations revealed that the pH sensitivity of 25Ag 2 O·75TeO 2 /Ti (3%) was significantly lower than that of 25Ag 2 O·75TeO 2 /SUS (12%). Ag 7 Te 4 observed in Ti samples had a higher Te fraction than Ag 2 Te observed in SUS samples. The stronger reducing ability of Ti compared to Fe in SUS facilitated the reduction of Te 4+ ions to Te 0 , which subsequently reacted with Ag 0 . This observation supports the hypothesis that the pH sensitivity of Ag 7 Te 4 is lower than that of Ag 2 Te. Heat treatment of Ti on 25Ag 2 O·75TeO 2 /SUS resulted in a gray TiO 2 /Ti layer surrounded by ocher-colored precipitates, including the Ag–Te alloy. Increasing the Ti content in Ti/25Ag 2 O·75TeO 2 /SUS reduced its pH sensitivity. A 1:2 Ti weight ratio achieved a pH sensitivity of 5%, similar to 25Ag 2 O·75TeO 2 /Ti (3%). Dividing Ti into three sections eliminated the central TiO 2 /Ti layer, leaving only Ag–Te alloys and TeO 2 as the predominant materials. However, this structural modification had no discernible impact on the pH sensitivity. These findings suggest that Ag–Te alloys and TeO 2 can act as primary pH-responsive sites, with TiO 2 /Ti having no significant contribution. Since TeO 2 likely has a higher electrical resistivity than Ag–Te alloys, the observed low pH sensitivity results from that of the minor but electrically conductive Ag–Te alloys. Therefore, 25Ag 2 O·75TeO 2 /Ti is a promising candidate for developing KCl-leakage-free reference electrodes for pH sensors, offering low pH sensitivity. • The investigations revealed that the pH sensitivity of 25Ag 2 O·75TeO 2 /Ti was lower than that of 25Ag 2 O·75TeO 2 /SUS. • Ag 7 Te 4 observed in Ti samples has a higher Te fraction than Ag 2 Te observed in SUS samples. • Ag–Te alloys may act as the primary conduction path and pH-responsive sites. • 25Ag 2 O·75TeO 2 /Ti is an up-and-coming candidate for developing KCl-leakage-free reference electrodes.