Ethanol sensors based on zinc oxide synthesized by the chemical precipitation method

Abstract

We report the synthesis, structural characterization and ethanol vapor sensing performance of zinc oxide (ZnO) ceramic sensors prepared from a chemical-precipitation nanomaterial and commercial submicron ZnO powder. ZnO powder is synthesized by precipitation from zinc acetate using KOH as precipitant, dried and processed into gas-sensitive layers on a porous ceramic substrate with silver electrodes; reference sensors are prepared from industrial ZnO. Structural characterization (XRD, optical microscopy) indicates polycrystalline wurtzite ZnO; Scherrer analysis yields average crystallite sizes of ~270 nm (synthesized) and ~500 nm (commercial). Gas sensing testing is performed in a controlled measurement chamber under ethanol vapor partial pressure P_e = 37 Pa at operating temperatures from ~380 K to ~640 K. The commercial-powder sensor exhibits approximately two-times larger response across the tested temperature range, while the synthesized-powder sensor has higher baseline conductivity. The response peaks near ~ 600 K and decreases at higher temperatures. Differences are discussed in terms of grain size, chemisorbed oxygen coverage and inter-granular potential barriers affecting carrier transport. These results illustrate the complex interplay of microstructure and surface chemistry in ZnO ethanol sensing and highlight practical considerations for sensor fabrication and thermal activation.