The crystal structure of π-ErBO3: New single-crystal data for an old problem

Single crystals of the orthoborate π-ErBO3 were synthesized from Er2O3 and B2O3 under high-pressure/high-temperature conditions of 2 GPa and 800 °C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature. The title compound crystallizes in the monoclinic pseudowollastonite-type structure, space group C2/c, with the lattice parameters a=1128.4(2) pm, b=652.6(2) pm, c=954.0(2) pm, and β=112.8(1)° (R1=0.0124 and wR2=0.0404 for all data).

graphical abstractThe first satisfying single-crystal structure determination of π-ErBO3 sheds light on the extensively discussed structure of π-orthoborates. The application of light pressure during the solid state synthesis yielded in high-quality crystals, due to pressure-induced crystallization.Figure optionsDownload as PowerPoint slideResearch highlights
► High-quality single crystals of π-ErBO3 were prepared via high-pressure-induced crystallization.
► At least five different space groups for the rare-earth π-orthoborates are reported.
► π-ErBO3 is isotypic to the pseudowollastonite-type CaSiO3.
► Remaining ambiguities regarding the structure of the rare-earth π-orthoborates are resolved.