High Temperature Operable Low Humidity (10 to 20% RH) Sensor Using Spin Coated SnO2 Thin Films

The paper presents Tin oxide (SnO2) based low cost, high temperature operable resistive type low humidity (1020% RH) sensor. SnO2 thin films were prepared by spin coating 50 mu l of synthesized (SnCl2) solution on alumina substrate (1.44 cm(2)). Material characterization of the synthesized material was carried out using UV-Visible, SEM and XRD. To get films of higher thickness they were coated from 1 to 4 layers and annealed in the furnace at an optimized temperature of 550 degrees C for similar to 1 hour. Obtained SnO2 thin films were tested for change in resistance w. r. t. humidity from 10 to 20% RH at 200 degrees C and 300 degrees C to be used in boilers. Samples have low hysteresis (similar to 12%) with recovery time of about similar to 10 sec. They have shown good repeatability (5%). The sensitivity of tested films was found to increase with respect to number of SnO2 layers. Sensitivity of 2 layered film operating at 200 degrees C is 146 Omega% RH and that of 4 layered film is 314 O/% RH, likewise at 300 degrees C the sensitivity of the films are 165 Omega% RH and 323 Omega%RH respectively.