Grain Boundary Defects Induced Switching in Zn- Bi- Mo Ceramic
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.
David J. Fisher
M. El-Hofy "Grain Boundary Defects Induced Switching in Zn- Bi- Mo Ceramic", Defect and Diffusion Forum, Vols. 251-252, pp. 13-20, 2006