One-step synthesis of diopside (CaMgSi2O6) ceramic powder by solution combustion method

Abstract

We report the synthesis of diopside (CaMgSi2O6) ceramic powder, a multifunctional material, through an energy efficient, quick and one-step solution combustion (SC) method. Synthesis of diopside by SC method requires oxidizers, especially metal-nitrates, and a suitable fuel. However, unavailability of the silicon-nitrate makes the process of diopside formation by SC method challenging, which forces researchers to synthesize diopside by alternate high temperature solid state reaction route. Here, we demonstrate a simple way to overcome this difficulty by using an extra amount of ammonium nitrate (AN, as the suitable oxidizer), but still using the fumed-silica (an economical ceramic powder) and the solution of Ca-nitrate, Mg-nitrate and the fuel. A systematic investigation was carried out using different extra amounts (0, 5 or 10 mol) of AN, in combination with stoichiometric amounts of one of the three chosen fuels, viz., urea, glycine and alanine. For a specific combination of the fuel and extra oxidizer, namely ‘alanine and 10 mol of AN’, we observed the formation of nano-crystalline diopside phase, which generates enough heat for the incorporation of Si atoms from the SiO2 precursor into diopside phase directly during the combustion process in one-step. This one-step process does not require any extra high temperature calcination step, thereby saving time, cost and complex equipments, whereas all other powders synthesized using other fuels require an extra calcination step, although the calcination temperature is low (≤ 900 °C), for crystalline diopside phase formation. Hence, our work demonstrates the one-step synthesis of diopside nanopowders by SC method through the direct use of the earth abundant SiO2 ceramics.