Lead-free ferroelectric ceramics

Ferroelectric ceramics has found a large variety of applications in electronics since mid-1940-s, when the ferroelectric origin of high dielectric and piezoelectric performance of barium titanate (BT) ceramics was realized. A few years later, ferroelectricity was found in a great number of other perovskites including alkali niobates (e.g. sodium-potassium niobates - KNN) and lead containing perovskites (e.g. lead zirconate-titanates - PZT). PZT ceramics still retain their leadership, especially in piezoelectric applications, due to their unsurpassed functional performance available in a wide range of temperature. A new revival of interest to lead-free ceramics has come lately with a nowadays tendency of phasing out lead containing elements in electronic devices since the special restriction directive was issued among European Union and other countries. The search for lead free piezoelectric alternatives with enhanced functional properties among complex oxides requires consideration of crystal structure, electronic structure, phase diagrams, and phenomenological models of ferroelectricity. Finally, the toxicity and cost of alternatives must also be taken into account. Currently, the leading candidates are coming from mixed perovskites with different crystal structures. These include KNN, BT, mixed bismuth-alkali titanates, and others. Further enhancement of functional properties and cost efficiency in lead-free ferroelectric ceramics can be achieved by employing advanced processing techniques, such as low-temperature powder synthesis, thick and thin film processing, texturing, etc. Our exploratory works on some of these cases include spray pyrolysis synthesis, variations of tape casting, spin coating film deposition, and others.