As the curve a and b shown in Fig. 5, the sensitivity of ZnO-A1 and ZnO-A2 sheet product to acetone gas was slowly increased with the increment of temperature below 180 C, but the sensitivity was with a sharp increment when the
temperature beyond 180 C, and reached the maximum value of 24.9 and 21.21 at 220 C, respectively. The optimum operating temperature was much lower to the results of ZnO, SnO2 and ZnSnO3 sensors to acetone gas reported in the literatures [25–28], in which the optimum operating temperature of these sensors was 300 C, and some were even above 300 C. For the rod-shape samples of ZnO-A3 and Zn-A4, the sensitivity to acetone gas was slowly climbed when the temperature below 200 C as Fig. 5c and d shown, and reached the maximum value of 16.42 and 14.89 at 220 C, respectively, which was in the shade compared with the sensitivity of the sheet ZnO product.