Bulk Crystal Growth and Properties of a (K,Na)NbO₃ Single Crystal by the Czochralski Method

Abstract

Environment-friendly (K,Na)NbO 3 (KNN) piezoelectric materials have been extensively studied in the past decade; particularly, bulk KNN single crystals are highly demanded in practical applications and fundamental studies. However, since the KNN solid-solution phase diagram is very complicated, it is still challenging to grow high-quality KNN single crystals. In this work, the growth of a KNN single crystal using the Czochralski technique was demonstrated. A KNN single crystal with dimensions of 13 × 13 × 40 mm 3 was successfully obtained. The grown crystal exhibits a good completeness, a high crystallinity, and a superior homogeneity. The leakage current is as low as 2.6 × 10 −8 A/cm 2 under an electric field of 30 kV/cm. This work establishes that the Czochralski method is a novel and effective approach in the future development of high-quality KNN-based single crystals.

Large Piezoelectricity Induced by Internal Stress in (K,Na)NbO3 Single Crystals

“…Although ferroelectric materials vary, the core functions have always been to enable devices with excellent performance outputs within a wide operational range in numerous electromechanical applications; therefore ferroelectric materials with high piezoelectric response and excellent stability are highly required, , flourishing research of exploring the origin of ultrahigh piezoelectricity and improving its piezoelectric performance as well as stability. − Numerous strategies have been proposed to acquire large piezoelectricity in ferroelectric materials, including the constructions of multiphase coexistence, polar nanoregions (PNRs), and electric-field-induced phase transition, etc. ,− Among them, Pb-based relaxor ferroelectric crystals have made remarkable progress in the design, research, and application of ultrahigh piezoelectricity. ,,, However, lead-free ferroelectrics with high performance and excellent stability are preferred over Pb-based materials due to environmental issues. Among all the lead-free ferroelectrics that are widely considered, the potassium sodium niobate ((K, Na)NbO 3 , KNN) family has drawn extensive attention owing to their high Curie temperature and excellent piezoelectric properties. ,− …”