THE INVESTIGATION ON THE FORMATION OF (K0.5Na0.5)NbO3 PEROVSKITE PHASE IN MECHANOCHEMICAL SYNTHESIS

Abstract

Lead-free (K0.5Na0.5)NbO3 (KNN) nanopowder with perovskite structure was synthesized by mechanochemical synthesis method successfully. In order to investigate the perovskite phase formation of KNN powders during the mechanochemical synthesis process, we set up three milling routes with different transmission ratios (Wv/Wp) acting on the mixed starting powders of Na2CO3, K2CO3 and Nb2O5 . KNN perovskite phase was not detected by XRD under the low transmission ratios -2 with the shock power of 273 W. When the transmission ratios was increased to -2.75 with the shock power of 683.4 W, KNN perovskite phase was formed after milling for 22 h. Based on these results, it has been found, that in shock mode process (SMP), that higher shock power is helpful for the formation KNN perovskite phase. The critical shock power P critical and critical weight-normalized cumulative shock energy [Formula: see text] in KNN system are discussed. Compared with SMP, when Wv/Wp = -3.5, in friction mode process (FMP), KNN perovskite phase was formed after milling for 5 h. It implies that FMP benefit the formation of KNN perovskite phase. The morphology of KNN powder was observed by transmission electron microscopy (TEM).