Investigation of the new P'3-Na0.60VO2 phase: structural and physical properties.

A new layered phase Na(0.60)VO(2) was synthesized by chemical deintercalation of sodium from the pristine compound O3-NaVO(2). The Na(0.60)VO(2) compound exhibits a distorted P'3-type oxygen stacking (AABBCC) with an average monoclinic unit cell containing a = 4.9862(14) A, b = 2.8708(8) A, c = 5.917(2) A, and beta = 104.36(3) degrees. A modulated structure was observed by transmission electron microscopy and X-ray diffraction (XRD) measurements. Indexation of the XRD pattern was achieved by using the q vector equal to 0.44b*, and the 4D superspace group C2/m (0 beta 0) s0 was then deduced. The specific heat measurement showed a strong correlated system with a gamma value of around 20 mJ x mol(-1) x K(-2). The electrical conductivity shows a semiconductor-like behavior with an activation energy of 0.52 eV. A paramagnetic behavior of the susceptibility is observed below room temperature with a Curie constant equal to C = 0.076 emu x K(-1) x mol(-1) x Oe(-1). To explain this small value, a model of pseudotriangular clusters of vanadium with a random distribution of V(3+) and V(4+) was considered.