Property-processing relationship in lead-free (K, Na, Li) NbO₃-solid solution system

There has been a significant driving force to eliminate the utilization, recycling, and disposal of ferroelectric ceramics with high content of toxic element (Pb). Recently, the ternary system of KNN-LT-LS has proven to be an outstanding lead-free piezoceramic with properties almost comparable to their lead-based counterpart, PZT. This study reports the effect of various processing conditions on the electromechanical properties of (K_0.44Na_0.52Li_0.04)(Nb_0.84Ta_0.10Sb_0.06)O₃ system. This includes powder processing, humidity, and exposure to oxygen rich environment during sintering. The Perovskite and Mixed-Oxide methods are used to prepare the stoichiometric powders. It will be shown that both processing methods are notably sensitive to the moisture of as received raw materials and the humidity of environment. Optimum results are obtained when the raw materials undergo a pre-heat treatment followed by formulating the desired composition in an inert atmosphere. The highest electromechanical properties are achieved when the ceramics are completely exposed to oxygen with a high flow rate. Sintered at 1150 °C for 1 h with an oxygen flow rate of 180 cm³/min, the KNN-LT-LS ceramics prepared by Perovskite and Mixed-Oxide routes have d ₃₃ ≥ 300 pC/N, \(\varepsilon ^{T}_{{33}} = 1865\), tan δ = 0.02, k ₃₃ = 0.65.