Enhancing Polyantimonic-Based Materials’ Moisture Response with Binder Content Tuning

Abstract

Humidity sensors are of huge importance in diverse domains. Several types of materials present a moisture-sensing capacity; however, frequently, their electrical response does not display time stability. Due to its high thermal stability, high ionic conductivity, and different conduction mechanism contributing to its overall conductivity, polyantimonic acid (PAA) is seen as a promising material for humidity-sensing devices. In the present work, crystalline PAA was obtained via a simple and safe hydrolysis technique using SbCl3 as a precursor. Bulky sensor samples were produced using different amounts of polyvinyl alcohol (10–20 wt.% PVA) as a binder. The obtained PAA solid sensors were tested at room temperature (RT) in order to evaluate their moisture detection/measuring ability in the relative humidity range 0–100%; the evaluation was carried out with electrical impedance spectroscopy. The sample’s structure and morphology were studied using diverse experimental techniques (porosimetry, scanning electron microscopy, X-ray diffraction analysis, and thermogravimetry analysis, etc.). The sensors’ electrical response was in line with the found structural and morphological features. The slope of the resistance variation with an RH percentage concentration between 1 kΩ and 1.5 kΩ was noted for all sensors (showing no changes with time) in the interval between 30 and 100% RH. A good repeatability and reproducibility of the evaluated sensors’ electrical response was observed: the ones that displayed a higher sensitivity were the ones with a high PVA binder content, higher than previously published results for PAA, as well as a very good time stability along the time and low hysteresis.