Influence of chemically synthesized powder addition on K0.5Na0.5NbO3 ceramic's properties

A new strategy to produce lead-free K0.5Na0.5NbO3 (KNN) piezoceramics with reliable and improved piezoelectric performance is presented for the first time. KNN powders were synthesized using two distinct synthesis routes: a mechanochemical activation-assisted solid-state route (KNNSSR) and a sol-gel modified Pechini method (KNNchem). KNNchem powders were mixed with KNNSSR at different weight ratios (0, 3, 5, 10 and 20 wt%), and the mixtures were conventionally consolidated and sintered at 1130 degrees C for 2 h. It was found that KNNchem powders influence crystal phase, microstructure and piezoelectric properties of the sintered pellets. Gradually increasing KNNchem content promotes the conversion of the undesired phase present in KNNSSR into the stoichiometric one. It is also proved that the addition of KNNchem between 5 and 10 wt% improves piezoelectric properties, eventually leading to a d(33) piezoelectric charge constant value of 113-115 pC/N. These values are among the highest reported for undoped KNN ceramics obtained by conventional sintering.