Cesium and Cesium-Lithium Selenates

The Cs 2 SeO 4 -H 2 SeO 4 -H 2 O and Cs 2 SeO 4 -Li 2 SeO 4 -H 2 O systems were studied at 30 °C as a basis for determining the conditions for formation of the compound Cs 4 LiH 3 (SeO 4 ) 4 , which has been observed to undergo a ferroelectric phase transition. The results of a solubility study were used to construct a pseudo-ternary cross-section for CsLiSeO 4 -CsHSeO 4 -H 2 O in the quaternary system Cs 2 SeO 4 -Li 2 SeO 4 -H 2 SeO 4 -H 2 O, which demonstrated that, in the region of crystallization of the compound of interest, a substance with the composition Cs 4 LiH 3 (SeO 4 ) 4 is actually formed. Attention was further paid to the following newly prepared compounds: cesium-lithium selenate hemihydrate, CsLiSeO 4 ·1/2 H 2 O, tricesium-lithium bis(selenate) hemihydrate, Cs 3 Li(SeO 4 ) 2 ·1/2 H 2 O and hydrogen tricesium bis(selenate) hemihydrate, Cs 3 H(SeO 4 ) 2 ·1/2 H 2 O, which were characterized by X-ray, spectral and thermoanalytical data.