Mechanochemical reaction in the K 2CO 3–Nb 2O 5 system

Abstract

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.