Crystal structure, spectroscopic, optical, thermal and magnetic studies of new orthoborate Sr2Co(BO3)2
Résumé
Single crystals of a novel distrontium cobalt diborate, Sr2Co(BO3)2, were successfully obtained from the melt at
1200 °C of the polycrystalline material. The powder of Sr2Co(BO3)2 compound was synthesized using standard
solid state reaction at 850 °C. The refinement of the structure shows that Sr2Co(BO3)2 crystallizes in the monoclinic
cell with the space group C2/m. The crystal structure is built from [CoO6] octahedra linked to [BO3] triangles
by the vertices and to the SrO9 polyhedra by sharing two faces. The infrared analysis confirms the existence
of BO3 vibrations group’s. The calculated gap energy is Egap ¼ 3.5eV for indirect gap model and Egap ¼ 3.75eV for
direct gap one. The magnetic measurements show that antiferromagnetic interactions are predominant in the
studied borate. The high temperature X-ray diffraction and the differential scanning calorimetry allow to observe
two anomalies in the temperature range of 400–800 °C which correspond to the phase transitions of Sr2Co(BO3)2.