Crystal structure and electrical properties of K₂P₄W₁₂O₄₄, the m=6 member of the series of low-dimensional conductors K_x(PO₂)₄(WO₃)_2m

Abstract

A new member, m=6, of the series K_x(PO₂)₄(WO₃)_2m has been isolated and studied by single crystal X-ray diffraction and electrical transport measurements. The structure corresponds to that of the MonoPhosphates Tungsten Bronzes with hexagonal tunnels (MPTBh's). It has been solved and refined to conventional R=0.0268 with 2342 independent reflections with I>3σ(I). The unit cell is monoclinic (space group P2₁/m) with a=6.6736(2), b=5.3543(3), c=11.9005(5) Å, β=92.615(3)°. The oxygen surroundings of K, P and W atoms are described and compared with those of other members of the series including Pb-, Na- and K-based analogues. Electrical properties and correlations with structural data are discussed. Large magnetoresistance effects have been observed at low temperature and assigned to possible CDW instabilities.

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