Investigation of Lower Local Symmetry for ZnO in Nanocrystalline Form.
Abstract
ZnO has been investigated by Mössbauer(^67Zn) technique in both powder and nano-crystalline form for particle sizes between 5 and 25 nm. The experimental data suggest loss of the axial symmetry characteristic of the Wurtzite structure, in contrast to single crystal, through the manifestation of asymmetry parameter η of the order of 0.3 in the ^67Zn Nuclear Quadrupole Interaction at ambient pressure in both the powder and the nanomaterial. The instability in zinc position has been corroborated by both Hartree-Fock Cluster investigations and LAPW band structure calculations which indicate that it takes relatively little energy to move the Zn ion off the symmetry axis and that a displacement of about 0.003Åcan explain the values of η of the order observed. This finding may explain differences in luminescence properties between nano-sized Phosphors and their bulk counterparts if substitutional impurities behave in the same way as the Zn ion. Neutron diffraction studies in pressed pellets and powder of ZnO do not rule out as small a displacement as 0.003ÅX-ray diffraction measurements using Synchrotron radiation would be helpful in the future to try observe the small displacements suggested by Mössbauer measurements and theory.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1998
- Bibcode:
- 1998APS..MAR.I2001P