Effect of ZrO2 Coating Thickness on Capacitive Sensor Performance in Conductive Liquid Media

This study presents a capacitive sensor with a zirconium oxide (ZrO2) coating for real-time measurement of component concentration in liquid media. The ZrO2 layer was formed on stainless steel electrodes by magnetron sputtering, and its structural, morphological, and chemical properties were characterized using SEM, EDS, FTIR, and XRD. It was found that increasing coating thickness results in more continuous and highly crystalline layers, while reducing the influence of the substrate on surface properties. The performance of the capacitive sensor was evaluated by analysing the dependence of capacitance on frequency and NaCl concentration. The results show that the thickness of the ZrO2 layer has a significant influence on sensor sensitivity and measurement stability. A thinner layer (~2 µm) provides higher sensitivity but is more affected by parasitic effects, while thicker layers improve measurement stability at the expense of reduced sensitivity. An optimal trade-off between sensitivity and stability is achieved at a ZrO2 layer thickness of approximately 4 µm, ensuring sufficient sensitivity and good measurement repeatability. The results indicate that ZrO2-modified capacitive sensors are a promising technology for monitoring liquid quality, particularly in environmental protection and industrial process control.