Journal de la science des matériaux et des nanomatériaux

Abstrait

Ab Initio Structure Determination Of A Novel Mixed Valence Transition Oxide La0.5 Cd0.125 Zr0.125S0.76 N0.125 O0.25 Via Powder X-Ray Diffraction And Study The Electrical Property

Parashuram Mishra

The present work deals with the ab initio structure determination of the heavy metal framework La0.5.Cd0.125.Zr0.125.S.0.76.O 0.25.N 0.125 from precession electron diffraction intensities The metal framework of the compound was solved in this investigation via direct methods from hk0 precession electron diffraction intensities recorded with a Philips EM400 at 100 kV. A subsequent (kinematical) least-squares refinement with electron intensities yielded slightly improved co-ordinates for the 6 heavy atoms in the structure. Chemical analysis of several crystallites by EDX is in agreement with the formula La0.5.Cd0.125.Zr0.125.S.0.76.O 0.25.N 0.125. Moreover, the structure was independently determined by Rietveld refinement from X-ray powder data obtained from a multi-phasic sample. The compound having orthorhombic crystal system space group Pcnb with refined lattice parameters a=10.3617,b=10.3124,c=10.5490, and v=1192.64Å^3. Comparison of the framework structure from electron diffraction with the result from Rietveld refinement shows an average agreement for the heavy atoms within 0.09A ˚ . The titled compound was prepared from mixture of La2(CO3)3, Zr(NO)2,andCdSO4 by solid state reaction with full thermal decomposition at 1000°C. Rwp = 0.0417, Rp = 0.032 and Rp = 0.082. The structure factors F0=3032 and Fc=3031. The morphology of the crystal has been determined by SEM.