The synthesis and characterisation of lead-free piezoelectric ceramics

Abstract

With a growing awareness of the environmental and health hazards of lead, there has been renewed interest in developing lead-free alternatives to lead zirconate titanate (PZT), which currently dominates the market for piezoelectric materials. Some of the most promising lead-free piezoelectric materials are those based on potassium sodium niobate (KNN). This project involved the fabrication and characterisation of lithium-doped KNN ceramic, which has been reported to show excellent piezoelectric properties. Samples containing 0-9 mol% Li were synthesised by a conventional mixed oxide method, before their key functional properties were analysed. The addition of lithium was found to promote grain growth within the microstructure, resulting in a denser ceramic. A phase transformation from the orthorhombic to tetragonal crystal structure was also identified. Optimum piezoelectric properties were observed in KNN samples containing 7 mol% Li (k\(_p\)=0.33, k\(_t\)=0.37, d\(_{33}\)=126 pC/N). Further optimisation of the fabrication route and continued investigation into the most effective dopants could potentially bring KNN on a par with many commercial lead-based ceramics.