A Structural and ac Conductivity Study on Li Doped ZnO

In the present work, the incorporation of Li in a wurtzite ZnO host synthesized through a chemical route has been studied experimentally. Starting with Yoshio's model, [K. Yoshio, A. Onodera, H. Satoh, N. Sakagami and H. Yamashita, Ferroelectrics, 264, 133 (2001)] structural refinement of the powder diffraction data suggests that Li has a mixed occupancy at both the substitutional 2b (≈1.2%) and interstitial 2a (≈12.6%) Wykoff sites. In comparison with a pure ZnO sample, the net result appears to be an overall expansion of the unit cell by ∼0.07% along both a and c -axes. Temperature dependant ac conductivity measurements carried out using a two electrode assembly and the influence of superimposed dc bias suggest that the conduction may be governed by both the presence of interstitial Li and polar defect complexes also. The grains seem to respond more to an applied dc bias (an order of magnitude change in resistivity) than grain boundaries.