Synthesis, Crystal Structure, and Thermal Behavior of the Rare Earth Sulfates (H₅O₂)M(SO₄)₂ (M = Ho, Er, Y)

Abstract

The compounds (H5O2)M(SO4)2 (M = Ho, Er, Y) were obtained from the metal oxides M2O3 (M = Ho, Er, Y) using diluted sulfuric acid (80%). The crystal structure of the isotypic compounds has been determined from single-crystal data by direct and Fourier methods [tetragonal, I41/amd (No. 141); (H5O2)Ho(SO4)2, a = 6.9140(5) Å, c = 17.246(2) Å, R = 0.013; (H5O2)Er(SO4)2, a = 6.8967(7) Å, c = 17.166(2) Å, R = 0.012; (H5O2)Y(SO4)2, a = 6.8875(7) Å, c = 17.159(2) Å, R = 0.016]. The characteristic feature of the crystal structure is a network of edge-sharing [MO8] trigon dodecahedra and [SO4] tetrahedra providing channels along [111] which are occupied by disordered H5O2 + ions. In situ X-ray powder investigations exhibit that the compounds are also formed as intermediate phases during the reaction of the hydrogen sulfates M(HSO4)3 (M = Ho, Er, Y) with water. According to DSC measurements and temperature-dependent powder diffraction studies, the thermal decomposition of the title compounds follows a two-step mechanism. Around 150 °C, two molecules of water are driven off, yielding M(HSO4)(SO4) (M = Ho, Er, Y), and finally, at 320 °C, H2SO4 (H2O + SO3) is released to give the anhydrous sulfates M2(SO4)3.

Inorganic Lanthanide Compounds with Complex Anions

“…The hydrogensulfates of the rare-earth elements are very moisture sensitive. As can be seen with the help of time-resolved X-ray powder diffraction, Er(HSO 4 ) 3 reacts with H 2 O in the first step to form H 5 O 2 Er(SO 4 ) 2 and finally Er 2 (SO 4 ) 3 ·8H 2 O (Figure ) . Single crystals of H 5 O 2 Er(SO 4 ) 2 and the isotypic compounds with Gd, Ho, and Y grow from sulfuric acid (80% H 2 SO 4 ) so that the structure is known .…”

“…As can be seen with the help of time-resolved X-ray powder diffraction, Er- (HSO 4 ) 3 reacts with H 2 O in the first step to form H 5 O 2 Er(SO 4 ) 2 and finally Er 2 (SO 4 ) 3 ‚8H 2 O (Figure 51). 496 Single crystals of H 5 O 2 Er(SO 4 ) 2 and the isotypic compounds with Gd, Ho, and Y grow from sulfuric acid (80% H 2 SO 4 ) so that the structure is known. 496 Opposite to H 3 OCe(SO 4 ) 2 ‚H 2 O, 497 which has the same composition, in H 5 O 2 Er(SO 4 ) 2 the H 3 O + ion and the water molecule are joined to a H 5 O 2 + ion with a very short hydrogen bond (Figure 52b).…”

“…496 Single crystals of H 5 O 2 Er(SO 4 ) 2 and the isotypic compounds with Gd, Ho, and Y grow from sulfuric acid (80% H 2 SO 4 ) so that the structure is known. 496 Opposite to H 3 OCe(SO 4 ) 2 ‚H 2 O, 497 which has the same composition, in H 5 O 2 Er(SO 4 ) 2 the H 3 O + ion and the water molecule are joined to a H 5 O 2 + ion with a very short hydrogen bond (Figure 52b). The Er 3+ ions are in a dodecahedral surrounding of oxygen atoms (Figure 52a).…”

“…Er(SO 4 ) 2 loses two molecules of water in the first step yielding Er(HSO 4 )(SO 4 ), which finally decomposes to Er 2 -(SO 4 ) 3 496. In the hydrogensulfates Y(HSO 4 ) 3 ‚H 2 O493 and Gd(HSO 4 ) 3 ‚H 2 O 494 the hydrogen atom is not part of an oxonium ion but located on the sulfate group.…”

Synthese und Kristallstruktur von Y(HSO4)3-I und Y(HSO4)3 · H2O

“…Colorless, plate like single crystals of Y(HSO 4 ) 3´H2 O grew from a solution of Y 2 O 3 in 85% sulfuric acid upon cooling. In the crystal structure of the tri-clinic compound (P1, Z = 2, a = 679.8(1), b = 802.8 (2), c = 965.9(2) pm, a = 79.99(2)°, b = 77.32(2)°, c = 77.50(2)°, R all = 0.0264) Y 3+ is surrounded by seven HSO 4 ± groups and one molecule of water. …”