Comparative study of thermal annealing effect on undoped and Mn-doped (K,Na)NbO3 nanofibers

The (K, Na)NbO3 (KNN)-based ceramics have been deemed one of the most promising lead-free piezoelectric materials replacing lead-containing ones. In our study, we have prepared both undoped and Mn-doped KNN nanofibers via the electrospinning method and investigated how the thermal annealing process affects their structural, crystallographic, and piezoelectric properties. X-ray diffraction measurements suggest that the crystallization occurs around 450 degrees C in these fibers, and with increasing annealing temperature, both undoped and Mn-doped nanofibers become granular with small grains forming along the fiber, accompanying the crystallization. Both exhibit increasing piezoelectric properties with annealing temperature based on the piezoresponse force microscopy measurements with Mn-doping, leading to a higher piezoelectric response.