Comparative Humidity-Sensitive Behaviour of Undoped and Acceptor-doped Barium Stannates

Abstract

Three samples, undoped barium stannate (BS), 10 atom% nickel-doped barium stannate (BSN10) and 10 atom% chromium-doped barium stannate (BSC10) were synthesized via solid state reaction route. The formation of single phase of these samples was confirmed by powder X-ray diffraction pattern analysis. These samples have a cubic crystal structure. The lattice parameter of samples BS and BSN10 are nearly the same, whereas that of sample BSC10 is smaller. The bulk density and grain size of the samples are in the order BSN10 > BS > BSC10 and BSC10 > BSN10 > BS, respectively. The resistance and capacitance of the samples at room temperature (31°C) were measured in the frequency range of 20 Hz - 1 MHz and the relative humidity (RH) range of 10–95%. Amongst these three samples, sample BS exhibits a superior response to humidity. The resistance of this sample changes by more than three orders of magnitude as RH changes from 10 to 95%. The response and recovery times of the samples BSC10 and BS are nearly the same (for sample BS, the response and recovery times are 44 and 76 s, respectively) whereas the response and recovery times for sample BSN10 are larger than those of samples BS and BSC10. Presence of physically adsorbed water on the surface of these samples has been revealed by Fourier Transform Infra-red (FTIR) spectroscopy.

Keywords:

• Perovskite oxide
• Barium stannate
• Humidity sensor
• FTIR