Abstract—Lead free piezoelectric single crystals of (K_0.5Na_0.5)NbO₃ and 0.5 wt%, 1.0 wt% and 1.5 wt% MnO2 doped (K_0.5Na_0.5)NbO₃ (KNN) were grown by high-temperature solution method using K₂CO₃– Na₂CO₃ eutectic composition as flux with addition of small amounts of boron oxide for lowering the melting temperature. The effect of the manganese dopant on the dielectric properties, surface morphology and the domain structure were investigated. The MnO₂-doped KNN crystals were found to exhibit higher dielectric permittivity when compared with pure KNN single crystal. Mn doping increases the dielectric constant and decreases the dielectric loss. A slight decrease in the orthorhombic to tetragonal phase transition temperature T_(O-T) and Curie temperature T_C has been observed in manganese-doped KNN single crystals. From SEM and AFM analysis, the domain size of KNN–Mn crystal was found to be of the order of 5–13 μm at room temperature which is smaller than that of the pure KNN crystal (20–30 μm).

Index Terms—Ferroelectric, defect, KNN, piezoelectric, single crystal etc.

R. Saravanan and M. Chitra are with the Crystal Growth Centre, Anna University, Chennai.
D. Rajesh is with the G.T. Sollar Cell, China. S. V. Rajasekaran is with the Govement Arts and Science College, Dharmapuri.
R. Perumal is with the Hanyang University, Seoul, South Korea.
R. Jayavel is with the Centre for Nanoscience and Technology, Anna University, Chennai (e-mail: rjvel@annauni.edu, Tel.: +91-44-2235 8328, fax: +91-44-2230 1656).

Cite: R. Saravanan, D. Rajesh, S. V. Rajasekaran, R. Perumal, M. Chitra, and R. Jayavel, "Crystal Growth and Dielectric Property of Na_0.5K_0.5NbO₃ and Mn-Doped Na_0.5K_0.5NbO₃ Single Crystal Grown by Flux Method," International Journal of Applied Physics and Mathematics  vol. 2, no. 3, pp.  208-211, 2012.