Abstract:
The composition is based on a samarium sesquisulphide, it exhibits a samarium purity with respect to other rare earth metals of greater than 99% and it comprises at least one alkali metal or alkaline earth metal element, at least a portion of which is included in the crystal lattice of the said sesquisulphide. According to another embodiment, the composition is based on a sesquisulphide of samarium and of at least one rare earth metal which is solely trivalent and it comprises at least one alkali metal or alkaline earth metal element, at least a portion of which is included in the crystal lattice of the said sesquisulphide. According to a third embodiment, the composition exhibits a samarium purity such that the cerium content is less than 1%. The process consists in reacting samarium, trivalent rare earth metal and alkali metal or alkaline earth metal compounds with a gaseous mixture of hydrogen sulphide and of carbon disulphide.
Abstract:
The present invention relates to a composition based on a sulphur compound, zinc and optionally a transparent oxide, to a process for its preparation and to its use as a dye pigment. The composition of the invention is characterized in that it comprises a support based on at least one sulphur compound, and a zinc compound, deposited on the support and obtained by reaction of a zinc precursor with aqueous ammonia and/or an ammonium salt. The composition may also comprise a layer based on at least one transparent oxide deposited at the surface of the support and/or fluorine atoms. It may be prepared in particular by a process in which the support, a zinc precursor, aqueous ammonia and/or an ammonium salt and, if necessary, a transparent oxide precursor and a fluorinating agent are placed in contact and the zinc compound is deposited on the support and, where appropriate, the transparent oxide is precipitated on the said support.