Montedison S.p.a.

Paola Gherardi

Egon Matijevic

Titanates of barium, strontium, or mixed barium and strontium consisting essentially of solid, non-aggregated particles having diameters ranging from 0.05 to 1 micron and a narrow particle size distribution expressed by the polydispersity index, dw/dn, not greater than 1.20, where dw is the weight average diameter and dn is the number average diameter, said particles being essentially perfectly spherical with a total mean axial ratio of at least 0.93. These titanates are prepared by a process which comprises precipitating of a peroxidic precursor having the same morphological characteristics of the titanates. The peroxidic precursor is obtained by heating an alkaline solution comprising a complex of a titanium compound with a peroxidic compound, an M.sup.2+ compound, wherein M is Ba, Sr or mixtures thereof, and a compound Z capable of complexing with the M.sup.2+ ion oxidizable by the peroxidic compound under the conditions of reaction to produce soluble decomposition products and provide a homogeneous precipitation of the peroxidic precursor comprising titanium and M.sup.2+. Subsequently the precursor is heated to a temperature of at least 100.degree. C. to obtain the corresponding titanate having the above-indicated morphological characteristics.

Titanates in the form of spherical particles and process for preparing

Spherical particles having sizes below 1 .mu.m, or at maximum of 3.04 .mu.m, a narrow size size distribution consisting, or consisting essentially, of TiO.sub.2 coated by a uniform layer having a thickness up to 400 .ANG. consisting essentially .alpha.-, or .gamma.-Fe.sub.2 O.sub.3, or magnetite, or mixtures thereof, said particles being prepared by a process consisting, or consisting essentially, in the precipitation of the oxide from Fe (III) salt solutions on the surface of solid pre-formed TiO.sub.2 particles having a narrow size distribution and a number average diameter below 1 .mu.m or .ltoreq.3 .mu.m, the Fe (III) concentration being .ltoreq.40% by weight calculated on TiO.sub.2, the pH of the suspension ranging from 1.0 to 2.8, extremes excluded, by heating the suspensions to temperatures of from 80.degree. to 100.degree. C., and by aging them under such conditions for at least 30 minutes.

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Novara, Italy

Paola Gherardi