Super Nernstian pH sensitivity of excess cerium in Ce_2-xSr_x(Zr_0.53Ti_0.47)O_y sensing membranes for solid state pH sensors

This study aims to investigate the super Nernstian pH sensitivity of Ce_2-xSr_x(Zr_0.53Ti_0.47)O_y (CSZT) electrolyte-insulator-semiconductor (EIS) sensors with excess cerium content as a novel solid state device which can be used for detection of pH. We employed the X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and field-emission transmission electron microscopy to characterize the structural, morphological, chemical, and microstructural features, respectively, of these films as a function of the growth condition (strontium doping concentrations varied from 0, 5, 10, and 15%). The CSZT EIS device treated at the 10 mol% Sr condition exhibited the highest sensitivity of 93.15 mV/pH, the lowest hysteresis voltage of 1 mV, and the smallest drift rate of 0.32 mV/h among these conditions. This result may be attributed to the optimal Sr content in the CSZT creating a high content of Ce³⁺ ions, producing a higher surface roughness and forming the neutral oxygen vacancies.