Patent ID: 7232557

Claim:
A method for preparation of magnetic spinel ferrites from layered double hydroxide precursors comprising the steps of: adding an alkali solution slowly dropwise to a mixed salt solution under an N 2 atmosphere until the pH of the mixture of said alkali solution and said salt solution reaches about 7 to about 12, resulting in the production of a precipitate; aging said precipitate for about 5 to 25 hours at about 20° C. to 65° C.; cooling said precipitate by adding N 2 -saturated deionized iced water; filtering and washing said precipitate with N 2 -saturated deionized water to neutrality; further filtering and washing with ethanol 2 to 4 times at about 0° C. to about 10° C., resulting in a gelatinous precipitate; drying said gelatinous precipitate at room temperature to produce Me 2+ —Fe 2+ —Fe 3+ layered double hydroxides (LDH) precursors; and calcining said LDH precursors in air at about 850° C. to about 1150° C. for about two to seven hours with a temperature increasing rate of about 2° C. to about 15° C./min to obtain magnetic spinel ferrites, wherein said alkali solution comprises about 1.0 M to about 2.5 M of sodium hydroxide, up to 1.7 M of sodium salt, and N 2 -saturated deionized water, wherein said mixed salt solution comprises about 0.1 M to about 0.6 M of Me 2+ , about 0.1 M to about 0.6 M of Fe 2+ , and about 0.1 M to about 0.6 M Fe 3+ , and wherein said Me 2+ has similar ionic radius as said Fe 2+ and is one or two divalent metal ions selected from the group consisting of Mn 2+ , Zn 2+ , Cu 2+ , Ni 2+ , Mg 2+ or Co 2+ , and wherein the sum of the moles of said Fe 2+ and said Fe 3+ is twice that of said Me 2+ .