CRYSTAL-STRUCTURE OF HIGH-TEMPERATURE STRONTIUM PYROVANADATE

Single crystals of the high-temperature phase of strontium pyrovanadate, alpha-Sr2V2O7, were grown from a melt in the Bi-Sr-V-O system. This compound crystallizes in the triclinic system in space group P1BAR (#2) with a = 7.0936(4) angstrom, b = 12.986(2) angstrom, c = 7.046(1) angstrom, alpha = 93.78(1)-degrees, beta = 90.877(7)-degrees, gamma = 99.447(7)-degrees, V = 638.6(1) angstrom3 and Z = 4. The structure can be described as the packing of four Sr2V2O7 layers that are approximately normal to the b axis or as the stacking of two zigzag chains. Two different types of (V2O7)4- anions are present. Three reported X-ray powder patterns are indexed with the cell parameters from this work. The alpha-to-beta polymorphic transition temperature is about 645-degrees-C.