Effect of different donor dopants on the seed-free solid-state crystal growth of potassium sodium niobate

Seed-free solid-state crystal growth (SSCG) is a developing technique to produce lead-free potassium sodium niobate (KNN) single crystals with the advantage of expeditious growth rates. The fundamental mechanism for seed-free SSCG is abnormal grain growth, which can be promoted through the inclusion of a precise concentration of an A-site donor dopant in KNN. To date, Ba2+ and Bi3+ have been utilised to grow centimetre-sized KNN single crystals with piezoelectric properties equivalent to traditional melt growth techniques. This research explores a broad range of potential donor dopants in (K0.5Na0.5Li0.006Dx)NbO3 (where D = Ba2+, Ca2+, Sr2+, Pb2+, Bi3+, La3+, Ce3+,4+ and Pr3+,4+) to determine disparities in abnormal grain growth behaviour and the critical parameters that enable substantial single crystal growth. The incorporation of different donor dopants influences the grain growth behaviour, single crystal sizes and preferential crystallographic orientations. This inspires future research to explore different compositions and techniques to improve the KNN crystal sizes and piezoelectric properties and addressing other challenges. These efforts are essential to improve the maturity of seed-free SSCG, making it industrially viable and a genuine alternative to costly single crystal growth techniques.