The preparation, crystal structures and some properties of californium oxysulfate and oxysulfide

Abstract Californium oxysulfate (Cf2O2SO4) has been prepared by calcination of Cf(III)-loaded Dowex resin beads or hydrated Cf2(SO4)3 in air at 700–800°C. At temperatures above 860°C, the oxysulfate decomposed to the sesquioxide. Calcination of the hydrated californium sulfate or the californium oxysulfate salt in atmospheres containing hydrogen, or in vacuum, at 800°C produced the oxysulfide (Cf2O2S). It was observed that the californium oxysulfide could be reoxidized to the oxysulfate by reheating the former product in air at 800°C. The decomposition of the oxysulfate and the oxysulfide to the sesquioxide by heating in air was found to be dependent on both the duration and the temperature of the calcination process. Examination of oxysulfate samples stored at ambient temperatures as a function of time showed that self-irradiation initially causes a loss in crystallinity and subsequently a partial decomposition to the sesquioxide. Lattice parameters for the oxysulfate and oxysulfide were derived from X-ray data. The lattice constants for the orthorhombic oxysulfate are: a 0 = 4·187 ± 0·002 A , b 0 = 4·072 ± 0·002 A and c 0 = 13·009 ± 0·006 A . The cell dimensions for the trigonal oxysulfide are: a 0 = 3844 ± 0·002 A and c 0 = 6·656 ± 0·004 A .