Synthesis, crystal structures and physical properties of two new sulfates KYb(SO4)2·H2O and KYb(SO4)F2

Highlights: • New compounds KYb(SO₄)₂·H₂O and KYb(SO₄)F₂ was synthesized by a conventional hydrothermal method. • The compounds exhibit a high thermal stability. • Both of compounds display a similar paramagnetic behavior down to 2K. • PXRD patterns at the temperature range of 80–850°C are investigated. Two new potassium ytterbium sulfates KYb(SO₄)₂·H₂O and KYb(SO₄)F₂ have been obtained by a conventional hydrothermal method, which are found to crystallize in the monoclinic system with space group P2₁/n and P2₁/m, respectively. KYb(SO₄)₂·H₂O features a three-dimensional open framework built by isolated YbO₄ polyhedra and SO₄ tetrahedra, while KYb(SO₄)F₂ exhibits a zigzag-chain structure built by YbO₄F₄ polyhedra running along [010] direction. Magnetic measurements indicate that both of two compounds display a paramagnetic behavior down to 2K with a dominant antiferromagnetic interactions between ytterbium ions. TGA and temperature-dependent PXRD measurements verify the excellent thermal stability of their frameworks. Solid-state UV–vis–NIR diffuse reflectance spectra show that they have wide optical band gaps of 4.95eV and 5.36eV, respectively.