Crystal structure, dielectric properties of (K_0.5Na_0.5)NbO₃ single crystal grown by flux method using B₂O₃ flux

Abstract

Abstract Lead free piezoelectric single crystals of sodium potassium niobate (K 0.5 Na 0.5 )NbO 3 (KNN) were grown by high‐temperature solution method using two different fluxes; one with a mixture of NaF and KF and other with addition of B 2 O 3 along with the mixture. In the present study, the growth of KNN crystals without B 2 O 3 flux and the same with B 2 O 3 flux were compared. It was found that additions of small amounts of B 2 O 3 lowered the melting temperature of the solid solution and enabled better dielectric properties. Phase analysis showed that all samples were crystallized in pure orthorhombic perovskite phase. AFM morphological studies showed that the addition of B 2 O 3 flux increased the roughness of the grown crystal. Further, addition of B 2 O 3 flux slightly decreased the orthorhombic to tetragonal phase transition temperature T (O—T) and the Curie temperature T C . The ferroelectric behaviour of KNN single crystal has been investigated at room temperature. The crystal grown using B 2 O 3 flux exhibited a remanent polarization (P r ) ∼ 32 μC/cm 2 and coercive field (Ec) of ∼11.8 kV/cm whereas the crystal grown without the use of B 2 O 3 flux had a remanent polarization (P r ) ∼ 36 μC/cm 2 and coercive field (Ec) of ∼14.6 kV/cm.