Investigation into the synthesis of reduced vanadium phosphate has led to the formation of a new form of the barium vanadium (III) pyrophosphate compound (\beta-\mathrm{BaV}{2}\left(\mathrm{P}{2} \mathrm{O}{7}\right){2}). It is a polymorph of the previously known (\mathrm{BaV}{2}\left(\mathrm{P}{2} \mathrm{O}{7}\right){2}), which is now labeled as the (\alpha)-phase. The title compound crystallizes in the (P \cdot 1) (No. 2) space group with (a=6.269) (1) (\AA, b=7.864) (3) (\AA, c=6.1592) (9) (\AA), (\alpha=101.34(2)^{\circ}, \beta=105.84(1)^{\circ}), and (\gamma=96.51(2)^{\circ}). The structure consists of corner-shared (\mathrm{VO}{6}) octahedra and (\mathrm{PO}{4}) tetrahedra that are connected in (\mathrm{V}-\mathrm{O}-\mathrm{P}-\mathrm{O}-\mathrm{V}) and (\mathrm{V}-\mathrm{O}-\mathrm{P}-\mathrm{O}-\mathrm{P}-\mathrm{O}-\mathrm{V}) bonding arrangements. This interesting three-dimensional framework is characterized by seven types of intersecting tunnels, three of which are occupied by the barium cation, while the others are empty. It is important to know that one of the empty tunnels has a relatively large window with a minimum diagonal distance of (4.41 \AA), which facilitates a possible framework for a lithium ion insertion reaction. The barium atom has a 10 -coordination sphere, (\mathrm{BaO}{10}), in which the oxygen atoms can be viewed as forming two intersecting pseudohexagonal planes. (\boldsymbol{\beta}-\mathrm{BaV}{2}\left(\mathrm{P}{2} \mathrm{O}{7}\right){2}) appears to form at a relatively higher temperature than its polymorph, (\alpha) (\mathrm{BaV}{2}\left(\mathrm{P}{2} \mathrm{O}{7}\right){2}). A detailed structural analysis and structural comparison with the (\alpha)-phase, as well as a brief comparison with (\mathrm{SrV}{2}\left(\mathrm{P}{2} \mathrm{O}{7}\right)_{2}), are presented. O 1994 Academic Press, Inc.