The influence of different niobium pentoxide precursors on the solid-state synthesis of potassium sodium niobate

摘要

Two batches of K_(0.5)Na_(0.5)NbO_3 were prepared from the orthorhombic and monoclinic Nb_2O_5 polymorphs and potassium and sodium carbonates. The influence of the different Nb_2O_5 precursors on the solid-state synthesis of K_(0.5)Na_(0.5)NbO_3 was studied. To reduce the particle size, both types of Nb_2O_5 were milled prior to use. XRD and TEM analyses showed that the milled orthorhombic Nb_2O_5 was single phase;;however, after milling Hie monoclinic Nb_2O_5 consisted of large monoclinic particles and orthorhombic nanocrystals. The latter reacted with the carbonates to form (K_xNa_(1-x)NbO_3 solid solutions with varying K/Na molar ratios, while the orthorhombic Nb_2O_5 reacted to form a homogeneous solid solution olK_(0.5)Na_(0.5)NbO_3. Sintering of the two powder compacts resulted in different densification behavior and microstructure. This study shows the important influence of the ftt^Os precursor phase and the particle size distribution on the homogeneity and further densification of the potassium sodium niobate solid solution.