Synthesis routes for enhanced piezoelectric properties in spark plasma sintered Ta-doped KNN ceramics

Processing, microstructure, electrical properties and cytotoxic behaviour of lead-free 0.99K0.5Na0.5NbO3-0.01BiFeO3 piezoceramics prepared using Spark Plasma Sintering (SPS)

“…Monot-Laffez et al also employed a post annealing treatment in an oxygen flow which appears to be very efficient in improving the planar electromechanical coupling factor (kp) up to 50% for Ta-doped KNN and 60% when using an special synthesis route to improve compositional homogeneity. [11] However, the effect of post annealing treatment in the BF doped KNN system has not previously been reported.…”

High Piezoelectric Performance in Undoped (K,Na)NbO3 Piezoceramics over a Wide Range of Compositions

“…Characterized by an unusually high T C (∼400 °C) and a relatively good piezoresponse, the family of potassium–sodium niobates (K,Na)­NbO 3 (KNN) constitutes a particularly interesting candidate among the Pb-free alternatives . Similar to PZT, the KNN phase diagram also features several vertical composition-dependent phase transitions. , Above all, the one close to the middle composition was already considered favorable for enhanced piezoelectric performance from as early as 1959. ,− Consequently, most reports on both doped and undoped KNN mainly focus on the stoichiometry K = 50% and its surroundings ,− based on the assumption to be the most promising composition. More recent investigations on different compositions bring into question, however, the benefits of KNN MPB: Wu et al reported in 2008 a negligible composition dependence of KNN properties over a wide range of middle stoichiometries, while Li et al found only a relatively small increase in d 33 in 2012.…”