Effect of mesoporous structure on Bi3.25La0.75Ti3O12 powder for humidity sensing properties

Bi3.25La0.75Ti3O12 (BLT) powder is synthesized via a metal-organic decomposition (MOD) method, and mesoporous structure is formed in the BLT powder via nanocasting method. The humidity sensing properties of BLT and mesoporous BLT (M-BLT) humidity sensors are investigated at room temperature within the relative humidity (RH) range of 11-95%. The BET surface area of M-BLT powder (10.8 m2/g) is remarkably bigger than it of BLT powder (0.4 m2/g). The optimum working frequency of BLT and M-BLT humidity sensors are 100 Hz, and the impedance variation of M-BLT humidity sensor is about six orders of magnitude within the whole humidity range from 11% to 95% RH, which is six times more than it of BLT humidity sensor (only about one order of magnitude). Linearity of the M-BLT humidity sensor is obviously better than it of the BLT humidity sensor, and its maximum linear error is only 2% at 75% RH. The response time and recovery time of M-BLT humidity sensor are about 32 s and 68 s at 100 Hz. The results indicate that mesoporous structure is beneficial for enhancing the humidity sensing properties of materials, and nanocasting method would be one of important and effective approach for preparing high-performance humidity-sensing material.