# Influence of Na Additives on the Characteristics of Titania-Based Humidity Sensing Elements, Prepared via a Sol–Gel Method

## TL;DR

This study shows that adding sodium to titanium dioxide improves humidity sensor performance, with significant resistance changes observed at different sintering temperatures.

## Contribution

The paper introduces a sol–gel method to enhance humidity sensing using sodium-doped TiO2 with cerium ions.

## Key findings

- Sodium doping increases humidity sensitivity compared to undoped samples.
- Resistance variation reaches over five orders of magnitude for samples sintered at 400 °C.
- Sodium additives improve sensor performance at both 400 °C and 800 °C sintering temperatures.

## Abstract

Humidity sensing elements based on sodium-doped titanium dioxide (Na-doped TiO2) were prepared using a sol–gel method in the presence of cerium ions and sintered at 400 °C and 800 °C. Titanium (IV) n-butoxide and a saturated solution of diammonium hexanitratocerate in isobutanol served as starting materials. Sodium hydroxide and sodium tert-butoxide were used as inorganic and organometallic sodium sources, respectively. The influence of sodium additives on the properties of the humidity sensing elements was systematically investigated. The surface morphologies of the obtained layers were examined by scanning electron microscopy (SEM). Elemental mapping was conducted by energy-dispersive X-ray (EDX) spectroscopy, and structural characterization was performed using X-ray diffractometry (XRD). Electrical properties were studied for samples sintered at different temperatures over a relative humidity range of 15% to 95% at 20 Hz and 25 °C. Experimental results indicate that sodium doping enhances humidity sensitivity compared to undoped reference samples. Incorporation of sodium additives increases the resistance variation range of the sensing elements, reaching over five orders of magnitude for samples sintered at 400 °C and four orders of magnitude for those sintered at 800 °C.