Mechanochemical reaction in the K_2CO_3-Nb_2O_5 system

摘要

We studied the mechanochemical synthesis of KNbO_3, starting from a powder mixture of K_2CO_3 and Nb_2O_5. The milling experiments were designed with different ball-impact energies in order to investigate the mechanochemical reactions. X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, Raman spectroscopy and transmission electron microscopy were used to characterize the samples. Based on the results, we propose a mechanism for the mechanochemical reaction between K_2CO_3 and Nb_2O_5. The first stage of the reaction is characterized by the formation of an amorphous carbonato complex, which decomposes after prolonged milling at higher ball-impact energy giving rise to the crystallization of KNbO_3 and other niobate phases with a molar ratio K/Nb < 1. The reaction course is discussed and compared with the Na_2CO_3-Nb_2O_5 system.