Synthesis of Al₂O₃-ZrO₂-M_xO_y (M = Mg, La) complex oxide systems using electrogenerated reagents and their physicochemical properties

Abstract

A method for the synthesis of metal oxide precursors based on the electrogeneration of reagents in a coaxial electrochemical reactor without a membrane with electrodes substantially different in the surface area was proposed. The electrogeneration is accompanied by the subsequent hydrolysis of the products, the formation of primary particles due to the polycondensation of aquahydroxo complexes, and their further enlargement. In the coaxial electrolyzer-reactor, the flow of gas and electrolyte bubbles moves up and to the sides from the central electrode to form a vortex in the confined space. This makes it possible to distribute the components of the reaction mixture and to suspend more uniformly the formed particles of the solid phase in the liquid bulk due to the appeared turbulence. The introduction of Zr⁴⁺, Mg²⁺, and La³⁺ ions favors the formation of stable positively charged particles. The average particle size of alumina modified with oxides of other metals (Zr, Mg, and La) obtained using electrogenerated reagents was found to be 20-50 nm. Under thermal treatment of the synthesized systems (1100°C), complex phase transformations lead to the formation of spinel Al₂MgO₄ and stabilization of α-Al₂O₃ and tetragonal t-ZrO₂ stable at high temperatures up to 1600°C