CO Sensing Properties of La-added MgFe2O4 Powders

MgFe 2 O 4 , La addition, malic acid complex, CO, semiconductor gas sensor La-added MgFe 2 O 4 (MgFe 2-x La x O 4 , 0.05 x 0.20) and pure MgFe 2 O 4 powders were prepared using a malic acid complex, and their CO sensing properties were examined in dry air in the temperature range of 300-500 C. It was observed that when the measurement atmosphere was changed from air to CO, the electrical resistance of the MgFe 2 O 4 sensor decreased, whereas that of the MgFe 2-x La x O 4 sensor increased, indicating that the MgFe 2-x La x O 4 sensor is a p-type semiconductor. It was also observed that the addition of La significantly improved the CO sensitivity of the MgFe 2 O 4 sensor. Among the MgFe 2-x La x O 4 sensors examined, the MgFe 1.85 La 0.15 O 4 sensor exhibited the highest response to CO at 300 C, and its value was 11.2 times higher than that of the pure MgFe 2 O 4 sensor. However, the MgFe 1.85 La 0.15 O 4 sensor did not exhibit a rapid response or steady-state electrical resistance in a CO atmosphere at 300 C. Conversely, at 400 C, the MgFe 1.90 La 0.10 O 4 sensor exhibited a higher response to CO than the MgFe 1.85 La 0.15 O 4 sensor and showed a quick response and a steady-state resistance. Therefore, it can be concluded that the MgFe 1.90 La 0.10 O 4 sensor exhibited the best CO detection characteristics among the sensors examined.