Application of Iron Manganite Thick Films for Humidity Sensing

Abstract

Iron manganite (FeMnO3) thick film samples were obtained by screen printing four layers of thick film paste on alumina substrate with test PdAg electrodes. The paste was made by adding organic vehicles to iron manganite powder obtained by solid state synthesis of starting hematite (alpha-Fe2O3) and manganese carbonate (MnCO3) powders. SEM analysis of the sample surface revealed a porous structure with a uniform particle size distribution. The average resulting film thickness was 48. m. The change of impedance was monitored in a humidity chamber in the relative humidity range 30.90% at three working temperatures: 25, 50 and 75 degrees C in the frequency range 42 Hz to 1 MHz. With increase in relative humidity the measured impedance decreased, showing the greatest difference at lower frequency with a low time delay (below 3%) between absorption and desorption processes (hysteresis). The sensor response and recovery times were several seconds.