Preparation of ZnO powders by hydrazine method and its sensitivity to C₂H₅OH

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of C₂H₅OH, CH₃COCH₃, H₂, C₃H₈, 100 ppm of CO, and 5 ppm of NO₂) were measured at 300 - 400°C. The prepared ZnO nanopowders showed high gas responses to C₂H₅OH and CH₃COCH₃ at 400°C. The sensing materials prepared at the compositions of [ZnCl₂]: [N₂H₄]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses (S = R_a/R_g, R_a: resistance in air, R_g: resistance in gas) to 200 ppm of C₂H₅OH(S = 102.8-160.7) and 200 ppm of CH₃COCH₃ (S = 72.6-166.2), while they showed low gas responses to H₂, C₃H₈, CO, and NO₂. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.