K3Ln[OB(OH)2]2[HOPO3]2 (Ln=Yb, Lu): Layered rare-earth dihydrogen borate monohydrogen phosphates

Two isotypic layered rare-earth borate phosphates, K3Ln[OB(OH)2]2[HOPO3]2 (Ln=Yb, Lu), were synthesized hydrothermally and the crystal structures were determined by single-crystal X-ray diffraction (R3̄, Z=3, Yb: a=5.6809(2) Å, c=36.594(5) Å, V=1022.8(2) Å3, Lu: a=5.6668(2) Å, c=36.692(2) Å, V=1020.4(1) Å3). The crystal structure can be described in terms of stacking of Glaserite-type slabs consisting of LnO6 octahedra interlinked by phosphate tetrahedra and additional layers of [OB(OH)2]– separated by K+ ions. Field and temperature dependent measurements of the magnetic susceptibility of the Yb-compound revealed Curie–Weiss paramagnetic behavior above 120 K (μeff=4.7μB). Magnetic ordering was not observed down to 1.8K.