Super-fast response humidity sensor based on La0.7Sr0.3MnO3 nanocrystals prepared by PVP-assisted sol-gel method

La0.7Sr0.3MnO3 (LSMO) nanocrystals were prepared by polyvinylpyrrolidone (PVP)-assisted sol-gel method and characterized by a variety of characterization techniques. The humidity sensor based on LSMO nanocrystals was fabricated and its humidity sensing properties were investigated at room temperature (25 °C) within the relative humidity (RH) range of 11-95%. The optimum working frequency of the LSMO humidity sensor was 10 Hz and the impedance variation was about four orders of magnitude within the whole humidity range from 11% to 95% RH. The LSMO humidity sensor was of super-fast response speed, which was only about 0.8 s from 11% to 95% RH at 10 Hz. The super-fast response property may be ascribed to the strong hydrophilicity of LSMO nanocrystals. In addition, the LSMO humidity sensor was of good reproducibility, stability, small humidity hysteresis (4% RH at 75% RH) and a fast recovery speed (∼4.9 s). These results indicate the LSMO nanocrystals can be used as a novel humidity sensing material to fabricate high performances humidity sensors.