SYNTHESIS, STRUCTURE, AND PROPERTIES OF THE ORTHOBORATE SRCU2(BO3)2

The new orthoborate SrCu2(BO3)2 has been synthesized and its structure determined by single-crystal X-ray methods. It crystallizes in space group I42m in a cell of dimensions a = 8.995(1) Å, c = 6.649(1)Å, and V = 537.9(1) Å3 with Z = 4. The structure was determined from 604 independent reflections and refined to the final residuals R = 0.040 and Rw = 0.051. It is composed of CuO4 rectangles and BO3 triangles that are connected by sharing vertices and edges to form two-dimensional sheets; Sr atoms are interleaved between successive sheets. The compound decomposes at 970(3)°C to CuO and amorphous strontium borate; the CuO is reduced to finely divided Cu metal by heating at 300°C in flowing H2. The corrected molar susceptibility of the material is 2.16(3) BM at 22°C. © 1991.