Microstructure and Humidity‐Sensitive Characteristics of α‐Fe2O3 Ceramic Sensor

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Abstract
The microstructure and humidity‐sensitive characteristics of α‐Fe2O3 porous ceramic were investigated. Microporous α‐Fe2O3 powders were obtained by controlling the topotactic decomposition reaction of α‐FeOOH. Water vapor adsorption thermogravimetrical experiments were carried out in the relative humidity (rh) range 0% to 95% on the α‐Fe2O3 powder and the 900°C sintered compact. The microstructure was investigated by SEM, TEM, Hg intrusion, and N2 adsorption porosimetry techniques. The humidity sensitivity was investigated by the impedance measurements technique in 0% to 95% rh on the compacts sintered at 50°C steps in the 850° to 1100°C range. Humidity response was found to be affected by the microstructure, i.e., the characteristics of the precursor powders and sintering temperatures.