Nonlinear I-V characteristics in doped ZnO based-ceramic varistor

作者：Sedky A^*; Abu Abdeen M; Almulhem Abdalaziz A

来源：Physica B: Condensed Matter , 2007, 388(1-2): 266-273.

DOI：10.1016/j.physb.2006.06.149

• I-V
• ZnO
• Fe doping
• nonlinear
• ceramics
• varistor

Two similar sets of Zn1-xFexO ceramic samples with various x values (0.00 < x < 0.50) are prepared by two different heat treatments. The first set is quenched from sintering temperature down to room temperature, and the second is left in the furnace and slowly cooled to room temperature. These samples are examined by using X-ray diffraction patterns (XRD), scanning electron microscope (SEM) and DC electrical measurements. XRD data indicate that the replacement of Zn2+ ion by Fe3+ ion does not influence the Wurtzite structure of ZnO samples, and other well-known peaks are formed. The results of SEM indicate that no secondary phases are formed at grain boundaries, supporting the XRD results. It is also apparent that the average grain size decreases with increasing Fe content up to x = 0.10, followed by an increase at x > 0.30. With increasing Fe content, a nonlinear region, obtained from I-V characteristics, clearly appears and is shifted to higher fields. Furthermore, the nonlinear coefficients are generally increased by adding Fe up to x = 0.30, followed by a decrease at x = 0.50. Moreover, the values of the barrier heights are also generally increased with Fe up to x = 0.10 and kept unchanged with further Fe content. On the other hand, the electrical conductivities at room temperature are measured and their values are found to be decreasing with increasing Fe content, as compared to those of an undoped ZnO sample. Our results are discussed in terms of both point defects and intrinsic donors, which are produced by Fe doping in the ZnO ceramic system.

• 出版日期2007-1-15