Fig. 3From: High Methanol Gas-Sensing Performance of Sm2O3/ZnO/SmFeO3 Microspheres Synthesized Via a Hydrothermal MethodDifferent resolution SEM images of S1 (a1–a3), S2 (b1–b3), S3 (c1–c3), and S4 (d1–d3). e Schematic diagram of the formation process from S1 to S4Back to article page