Papers by Keyword: Non-Ohmic Characteristics

Abstract: Three Zinc Molybdenum ceramic samples doped Bi have been prepared according to the chemical formula (1-x) ZnO – 0.2MoO3 – xBi2O3, where (x = 0.2, 0.5, 1.0) mol %. The samples were studied at room temperature through X-ray Diffraction analysis, SEM, EDAX, I-V characteristics and C-V measurements. The results decleared the presences of two phases; ZnO as a major phase beside Bi2MoO6 as a minor phase. At lower Bi additions; Bi and Mo ions are highly segregated at the grain boundaries, while at higher additions more homogenous distribution for these ions inside the grain is observed. Some pores are observed around the batches of the minor phase and at the grain boundaries. The grain size is enlarged with increasing Bi addition; while the number and size of the pores are decrease. Creation of the pores is attributed to oxygen liberation from the surface of the sample during sintering. Formation of Schottky barrier is indicated via I-V and C-V measurements and attributed to Zn vacancies at the grain boundary. Interface potential barrier, donor density, interface state density and barrier width are decrease with increasing Bi addition. I-V characteristics revealed voltage switching. The switching voltage E0 decreases with increasing Bi addition and it is reproducible even after several on-off cycles.

Abstract: Four Zinc Molybdenum ceramic samples (S1-S4), have been prepared according to the chemical formula (1-x) ZnO - x (MoO3), where (x = 0.1, 0.2, 0.6, 0.8) mol %. The samples were studied through X-ray Diffraction analysis, SEM, EDAX, I-V characteristics at different temperature up to 200 οC and C-V measurements. X-ray results decleared that Mo contributes to the structure mainly substitution in place of Zn. Entrance of Mo into the structure increases the intensity and shifts the X-ray peaks to higher θ values. At lower additions, Mo is segregated along the grain boundaries in the form of short bars, while at higher additions, circular batches of Mo rich phase are appeared on the surface of the large ZnO grains. The formulation of Schottky barrier is indicated, in case of (x < 0.1) the barrier is attributed to the trapping of electrons by the defects at the grain boundaries, while at higher additions the barrier was attributed to the concentration gradient of Zn vacancies in the grain boundary region. The calculated barrier height and non-linearity coefficient α are (1.15, 1.12, 1.15 and 1.48) eV and (59.4, 22.5, 35 and 87) for the samples S1- S4 respectively. Going from S1 to S4, donor density Nd and density of the interface states Ns decrease from 3.81x 1018 to 0.46x1018 cm-3 and from 6.41x1012 to 2.52x1012 cm-2 respectively, while the width W(cm) of the potential barrier increases from the value 1.68x10-6 cm for S1 to the value 5.5x10-6 cm for S4 . The current processed via electron tunneling through the barrier.