Significantly Improved Humidity Performance of La²O³-Based Sensor Modified by Li⁺, Na⁺, and K⁺ Ions

The effects of Li+, Na+, and K+ ions loading on the humidity-sensing performances of La2O3-based humidity sensors were investigated in detail. Single-ion loading shows that Li+-loading greatly decreases the impedance in the low humidity range and thus has no effect on improving humidity-sensitive response. Na+-loading increases the sensitive response over four orders of magnitude but causes large hysteresis in the medium humidity range. K+-loading raises the sensitive response over four orders of magnitude with a smaller hysteresis loop. Significantly improved humidity performance of a large humidity-sensitive response of nearly five orders of magnitude, satisfactory response/recovery time, low hysteresis, and good linearity were achieved simultaneously by optimizing the ratio of Li+, Na+, and K+ ions. This work underscores that alkaline ion modifying is a facile method to improve the properties of humidity sensors.