Humidity sensing properties of Bi0.5(Na0.85K0.15)0.5Ti0.97Zr0.03O3 microspheres: Effect of A and B sites co-substitution

Bi0.5(Na0.85K0.15)0.5Ti0.97Zr0.03O3 (BNKTZ) sensing materials were successfully synthesized via a simple metal-organic decomposition method. Their morphological feature was characterized as regular shaped microspheres, and it was observed that a large quantity of nanoparticles with the size, of 50-100 nm were present on microspheres surfaces. The introduction of a small quantity of Zr4+ in, the reaction system was played an important role in the size-control. At room temperature, humidity, sensing properties of the BNKTZ were investigated in detail. At 100 Hz, the curve of impedance versus relative humidity (RH) was of good linearity and the variation of BNKTZ humidity sensor's impedance was more than four orders of magnitude when humidity changed from 11% to 95% RH. The response time and recovery time were found to be about 18 s and 60 s, respectively. Furthermore, the maximum, hysteresis was only 4% RH. Comparing with A site substituted materials, with the similar response and sensing range, the A and B sites co-substituted BNKTZ humidity sensor possessed lower impedance, better linearity and wider operating frequency. The results indicated that BNKTZ microspheres have broader application for fabricating high performance room temperature humidity sensors.