Growth mechanism and enhanced electrical properties of K0.5Na0.5NbO3-based lead-free piezoelectric single crystals grown by a solid-state crystal growth method

(K0.45Na0.55)0.94Li0.06NbO3 (KNLN) single crystals were grown by a solid-state crystal growth (SSCG) method. The effects of MnO2 and crystal orientation of the seeds on the KNLN single crystal growth were investigated. It is found that liquid phase and interfacial reaction mechanisms affect the crystal growth for the SSCG. Using the <110>-oriented KTaO3 crystal as seeds, prism-shaped KNLN-100xMnO2 (x = 0-0.02) single crystals with a dimension of ∼10 mm × 10 mm were successfully obtained. The electrical properties of such single crystals were affected with MnO2 addition. The resultant <100>-oriented KNLN single crystals exhibit excellent piezoelectric performances: Smax = 0.38% and d33*=995pm/V at Emax = 38 kV/cm, TC = 460 °C, superior to other KNN-based piezoceramics even exceed lead-based ceramics. This work indicates that the SSCG is a practicable approach to prepare high-performance KNLN lead-free piezoelectric single crystals.