Structure and formation mechanisms of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 particles under hydrothermal conditions

Abstract

(K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders were synthesized via hydrothermal method. The effects of different reaction conditions on crystal structure, micro-morphology and phase formation were analysed by XRD and SEM in detail. The results reveal that (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders with orthorhombic lattice structure are synthesized at 200?C for 18 h with the total initial alkali concentration of 8mol/l. The average particle size of synthesized powders is about 500-700 nm, which has regular cubic morphology with uniform distribution. Moreover, doping with La3+ and Sb5+ inhibits the crystal growth. The phase evolution of the powders revealed that the hydrothermal synthesis of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 underwent two steps, where an intermediate product of K4Na4Nb6O19? 9H2O was found in the early stage at 140?C. Based on the results, the formation mechanism of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders was proposed. It can be inferred that the crystal growth model of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 is dissolution-crystal growth-recrystallization with the characteristics of layered growth.