Design and Verification of Humidity Sensors Based on Magnesium Oxide Micro-Arc Oxidation Film Layers

Abstract

Humidity detection range is an important indicator for measuring the performance of humidity sensors, but semiconductor humidity sensors often face the problems of narrow detection ranges and insufficient detection sensitivities. In this paper, a magnesium oxide (MgO) humidity sensor based on micro-arc oxidation (MAO) technology was designed to solve these problems by simultaneously using impedance and capacitance as the response signals, as well as by normalizing the output of the two signals. The experimental results showed that the average output of the micro-arc MgO ceramic film, with impedance as the response signal, could reach 150 in the low relative humidity(RH) range (11.3–67% RH), which was much higher than its sensitivity in the high humidity range (< 1), and the film showed fast response (13 s) and recovery (61 s). Under high humidity conditions (67–97.3% RH), with capacitance as the response signal, the output of the micro-arc MgO was as high as 120. Therefore, the micro-arc MgO humidity sensor with impedance, and the sensor with capacitance as the response signal, demonstrated good stability in low humidity and in high humidity environments, respectively, indicating that the method of selecting appropriate response signals for different humidity environments can be applied to extend the humidity detection range of sensing material, and to improve the humidity detection capability of a sensor.

Effect of Nb5+ and In3+ Ions on Moisture Sensitivity of Electrospun Titanium/Tungsten Oxide Nanostructures: Microstructural Characterization and Electrical Response

“…The increase in physisorption controlled conduction mechanisms (due to the increase in RH in the environment) evidences the presence of hydronium (H 3 O + ) ions for the formation of a high density of H + protons as charge carriers, by the Grotthuss mechanism [33], Figure 6b). In this configuration, the instability of the hydronium chemical bond promotes the hopping transfer of a H + proton to the nearest water molecule.…”

Humidity Sensors, Major Types and Applications

“…Magnesium oxide (MgO) humidity sensor designed with micro-arc oxidation (MAO) technology gave better performance than semiconductor humidity sensors which are usually prone to narrow detection ranges and poor sensitivities for detection. It has the advantage of using both impedance and capacitance as response signals, giving an output of 150 in the low relative humidity (RH) range (11.3-67% RH) when impedance was the response signal, and an output 120 at high humidity range of (67-97.3% RH) with capacitance as the response signal [14].…”

Aligned Grid Shaped NiO Nanowires for Humidity Sensing at Room Temperature

“…The charge transport occurs when the H 3 O + releases a proton to a nearby H 2 O water molecule, ionizing it and forming another H 3 O + , resulting in the hopping of protons from one water molecule to another and decreases the sensor resistance. This process is known as the Grotthuss chain reaction, and it is assumed that it also represents the conduction mechanism in liquid water in higher RHs [34]. In other words, with the increase of the RH, the Grotthuss protontransfer process takes place, leading to the participation of NW-NW junctions and electrode-NW interfaces in the conduction.…”