ABSTRACTResistive type sensors using 10 mol% Hf-doped ceria and 10 mol% Zr-doped ceria, which had a single cubic phase obtained by solid state reaction, were fabricated and their sensing properties were investigated. The resistance and resistivity of the 10 mol% Hf-doped ceria or 10 mol% Zr-doped ceria were smaller than those of non-doped ceria. In the case of the same temperature of solid state reaction, the resistance and resistivity of the 10 mol% Hf-doped ceria were much smaller than those of the 10 mol% Zr-doped ceria. Furthermore, in the case of the same dopant, the resistance and resistivity of the sensor prepared from the solid state reaction at 1773 K were much smaller than those at 1673 K. The sensor using the 10 mol% Hf-doped ceria could be used as an oxygen gas sensor in wide oxygen partial pressure range and could be applicable to a λ sensor and a universal A/F sensor.
