HUMIDITY SENSOR USING POTASSIUM HEXAGONAL TUNGSTEN BRONZE SYNTHESIZEDFROM PEROXO-POLYTUNGSTIC ACID AND ITS RESISTIVITY CHANGE MECHANISM

We have found that potassium hexagonal tungsten bronze (K-HTB) synthes ized from potassium peroxo-polytungstate at low temperature (500 degre es C) shows a remarkable increase in resistivity in a humid atmosphere at room temperature, The mechanism of the resistivity increase by inc orporation of water was investigated by gravimetry, complex impedance spectroscopy, and powder XRD measurement. The powder XRD profiles indi cated that superlattice structure of the K-HTB emerges by incorporatio n of water. A layer structure model of the K-HTB was suggested from th ese results.