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|Title:||IR, EPR and magnetic susceptibility studies on xCuO-0.45B2O3-(0.55-x)As2O3 polycrystalline system|
|Authors:||Das, B B|
|Abstract:||The XRD studies on xCuO-0.45B2O3-(0.55-x)As2O3 polycrystalline system reveal that for 0.05≤x ≤0.30 the average particle sizes are in the range 192-249Å. The density values do not follow any regularity with mol% CuO. The chemical analysis results show the formation of Cul+ by reduction of Cu2+ in the matrix. The room temperature IR studies indicate the presence of Cu—O bond, planar [BO3/2] and tetrahedral [OAsO3/2] units in the matrix. Presence of B-O-B linkage is also identified at lower mol% AS2O3. DTA/TG result shows no characteristic structural phase transformation in the range room temperature to 900°C. The fairly low values of the small polaron radii indicate that the polaron is slightly localized on a particular site. The very low values of the magnetic susceptibility suggest weak paramagnetic behaviour of the specimens. The values of the exchange integrals of the small polaron are found to be fairly low. The values of the g- and A-matrices are found to be similar within the composition range studied, at 300 K and at 77 K, and also do not change significantly in the range 300-77 K. This result shows that the [O1/2-CuO4/2-O1/2] octahedra containing the paramagnetic site Cu2+ is not affected significantly with the change in composition as well as with temperature in the range 300-77 K. The EPR lineshape simulation of specimen SI at 77 K reveal that the paramagnetic Cu2+ ion is in a tetragonally distorted octahedron of six oxygen atoms, [O1/2-CuO4/2-O1/2], having D4h symmetry. There is significant out-of-plane π-bonding present in the octahedron, as a result, the square planar [CuO4/2] unit of the octahedron is highly "squeezed".|
|Appears in Collections:||IJC-A Vol.42A(07) [July 2003]|
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