Structure, phase transition and impedance of Zn1-xLixO(0.10≤x≤0.70) ceramic

Abstract

Structural transformations of Li-doped Zn1-xLixO(0.10≤x≤0.70) which was synthesized by solid state reaction was investigated. XRD carried out on powder specimens of the samples show that they are polycrystalline in nature with a hexagonal wurtzite structure having minor impurities. The result indicates the maximum limit of substitution of Zn atoms by Li is at x= 0.4. The lattice parameter a reduced from 3.01 to 2.99 Å while c reduced from 5.21 to 5.19 Å. Whereas the Zn-O bond length reduced from 1.88 to 1.87Å for the undoped, to x=0.60 for the doped, respectively. The c/a ratio is 1.73 and is almost constant for all samples. The grain size of the (100) peak of the undoped ZnO is 41.73 nm and that of x= 0.10 is 41.76 nm. For x= 0.2 to 0.70, the grain size is 41.72 nm indicating that the grain size is almost independent of doping. The SEM results indicate a variation of grain size from 2.18 to 5.15 µm for the undoped ZnO to x= 0.50, which shows increase in grain size and reduction in grain boundaries as doping increases. The results show that x = 0.50 has the highest grain size, highest transition temperature and the marks the solubility limit. DTA results indicate the structural phase transition temperature of the doped ZnO ranged from ~371 to ~409 K and increased as the amount of Li increases. A single arc is observed in all the impedance plots of the ZnO together with the presence of a relaxation process which is non Debye. The impedance data show reduced resistance with increase in lithium content. A general increase in dielectric constant with increase in lithium content is observed.