Effect of firing temperature on electrical and gas-sensing properties of Nano-SnO2-Based thick-film resistors

Nano-SnO2-based thick-film resistors were fabricated using screen printing technology. To study the effect of firing temperature, sensors were fired in the range 425-850 degrees C. A mixture of tetragonal and orthorhombic SnO2 was observed in the range 425-700 degrees C. Above 700 degrees C, the presence of majority tetragonal phase was observed. The sheet resistivity and TCR values were one to two orders of magnitude less than the reported values. Sensors fired at 750 degrees C showed the highest sensitivity and selectivity for H-2, CO, and LPG at 140 degrees C, 210 degrees C, and 180 degrees C, respectively, with a response and recovery time of 12 and 22 s.