Humidity sensitive characteristics of Zn2SnO4–LiZnVO4 thick films prepared by the sol–gel method

Thick film ceramic humidity sensitive layers composed of the Zn2SnO4–LiZnVO4 system were sintered using nanometer powders. The humidity sensitive powders prepared by the sol–gel route have the advantages of lower resistance in the low relative humidity (RH) range, better resistance-RH linearity and long-term stability compared with layers sintered from conventional solid state reaction powders. The impedance measurements at different operation frequencies indicate that the sensors sintered at 900 °C for 1 h have an optimum resistance-RH linearity at 1 kHz. scanning electron microscopy (SEM) micrographs of the grain structures and complex impedance analysis confirm that high performance of the sensitive layer is associated with a fine microstructure morphology, which is characterized by suitable rod shaped grains forming mesopores and by well distributed LiZnVO4 additives, forming a thin glassy surface covering.