Ferroelectric KNbO3 nanofibers: synthesis, characterization and their application as a humidity nanosensor

By virtue of its non-toxicity, high T _c, and non-linear optical and ferroelectric properties, one-dimensional (1D) potassium niobate (KNbO₃) may enable the development of numerous nanoscale devices. Despite the progress in 1D perovskite materials, preparing high aspect ratio KNbO₃ nanostructures is still a concern. This report presents the successful synthesis of ultra-long KNbO₃ nanofibers using a simple sol-gel assisted far-field electrospinning process. At optimized conditions, centimeters long, orthorhombic KNbO₃ nanofibers with an average diameter of 100 nm have been obtained. The nanofibers are composed of uniform grains densely stacked along the direction of the nanofiber axis. Due to large surface-volume ratio, a high sensitive humidity nanosensor based on KNbO₃ nanofibers displaying a logarithmic-linear dependence behavior of the conductance with the relative humidity (RH) was demonstrated. The conductance increases dramatically from 10^-10 ℧ to 10^-6 ℧ while RH varies from 15% to 95% at room temperature. In addition, the nanosensor exhibits excellent sensing performance, including ultrafast response (≤2 s) and recovery times (≤10 s), good linearity and reproducibility. Furthermore, the change in ferroelectric coercivity with respect to the RH and its effect in the sensing behavior were unveiled. This work could enable broad applications in the fields of environmental sensing and nano-electrical-mechanical systems.