HUMIDITY SENSITIVITY OF BETA-ALUMINA TYPE FERRITE FILMS

The thin films of K+-β- and β″-ferrites have been prepared by dipping-pyrolysis process using potassium tert-butoxide and iron naphthenate. The films exhibited a significant decrease in impedance with an increase in relative humidity. In addition, the magnitude in impedance changes at 25°C was two or three orders and increased with a rise in firing temperature from 600° to 1000°C; that is, with the progress of the crystallization of β and β″ phases. The thin films with the composition of K2O·6.1Fe2O 3 showed the reversible changes in impedance with the humidity changes. The 95% response time to the humidity change from 43% to 80% RH was 10 s for the film with 1 μm thick obtained at 1000°C. The response time was remarkably shortened in the form of thin film. © 1990.