Patent ID: 6770256
Filing Date: 2004-08-03
Classification: C01B,C01G,C01P,Y10S

Abstract:
A process for mechanosynthesizing a metal oxide having a perovskite or perovskite-like crystal structure, and a stoichiometric content of oxygen, and a high BET specific surface area, said metal oxide being selected from the group consisting of perovskites of the general formula ABO3; perovskite-like materials of the general formula [(ABO3)n+CyOz]; non-stoichiometric compounds derived from perovskite and having the general formula (ABO3âˆ’x); and non-stoichiometric compounds derived from perovskite-like materials and having the general formula [(ABO3âˆ’x)n+CyOz], wherein:A comprises at least one element selected from the group consisting of Al, Y, Na, K, Rb, Cs, Pb, La, Sr, Ba, Cr, Ag, Ca, Pr, Nd, Bi and the elements of the lanthanide series of the periodic table; B comprises at least one element selected from the group consisting of Al, Ga, In, Zr, Nb, Sn, Ru, Rh, Pd, Re, Os, Ir, Pt, U, Co, Fe, Ni, Mn, Cr, Ti, Cu, Mg, V, Nb, Ta, Mo and W; C represents at least one element selected from the group consisting of Ga, In, Zr, Nb, Sn, Ru, Rh, Pd, Re, Os, Ir, Pt, U, Co, Fe, Ni, Mn, Cr, Ti, Cu, Mg, V, Nb, Ta, Mo, W, Al, Y, Na, K, Rb, Cs, Pb, La, Sr, Ba, Cr, Ag, Ca, Pr, Nd, Bi and the elements of the lanthanide series of the periodic table; n represents an integer number between 1 and 10; 0y represents an integer number between 1 and 5; z represents an integer number between 1 and 5; said process consisting essentially of the steps of:a) subjecting a mixture of starting powders, which are in the form of oxides, hydroxides, carbonates, nitrates, or oxalates, and are formulated to contain the components represented by A, B and C in the formulas to a high energy milling sufficient to induce chemical reaction of the components and thereby directly mechanosynthesize said metal oxide in the form of a perovskite or a perovskite-like material having a nanocrystalline structure as determined by X-ray diffractometry; b) increasing the BET specific surface area of the metal oxide obtained in step a) by further subjecting said metal oxide to high energy milling under a humidified atmosphere to obtain a metal oxide having a high BET specific surface area.