Influence of trace lithium addition on the structure and properties of K0.5Na0.5NbO3-based single crystals

K0.5Na0.5NbO3 single crystal with trace amounts of lithium addition was grown by the seed-free solid-state crystal growth method. The Li addition is helpful for the growth of the crystals and improves the properties of the K0.5Na0.5NbO3 single crystals. A small amounts (0.2–0.3 at.%) of Li addition can trigger the formation of around 25% tetragonal phase. The occurrence of the phase transition may be due to the variety of the K/Na atomic ratio after Li substitution in both the Na and K sites. The optimum amount of Li addition in the crystal is 0.2–0.3 at.% in order to obtain a well performance K0.5Na0.5NbO3-based single crystal. The best electrical performance of these K0.5Na0.5NbO3-based crystals can be achieved as follows: d33 = 255 pC/N, tanδ = 1%, d*33 = 313 pm/V, and Pr = 26.1 μC/cm2, indicating that the structure and properties of K0.5Na0.5NbO3-based crystals grown by the seed-free solid-state crystal growth method can be closely affected by trace lithium carbonate addition.