Structural, FTIR spectra and optical properties of pure and co-doped Zn1-x-yFexMyO ceramics with (M = Cu, Ni) for plastic deformation and optoelectronic applications

Abstract

We report here a considered novel study on the structural, FTIR spectra and optical properties of pure and co-doped Zn_0.90-xFe_0.1M_xO with ((M = Cu, Ni and (x = 0.00, 0.10) and (0.00 < y < 0.20)) at different sintering temperatures T_s (T_s = 850 °C for series I and 1000 °C series II). Although the ZnO wurtzite structure is conformed for all samples, some secondary lines with little intensity are formed. But the number of these lines is higher for series I than for series II. The (c/a) value and U-parameter are almost constant for all samples, while Zn–O bond length L is slightly increased. The porosity and crystallite size are decreased by Fe, and also for (Fe + Cu) samples, and their values for series I are lower than for series II. The residual stress is tensile for most samples. Interestingly, the Young’s, rigid and bulk modulus, Poisson’s ratio and Debye temperature, obtained from FTIR analysis, are increased by Fe addition with a further increase for Fe + Ni) samples for both series. A ductile nature is obtained for pure, Fe and (Fe + Cu) samples; whereas a brittle nature is approved for (Fe + Ni) samples. On the other hand, the energy gap (E_g), residual lattice dielectric constant (ε_L) and carrier density N are increased by Fe addition, followed by a further increase for (Fe + Cu) samples, while the vice is versa for the inter-atomic distance R. For example, E_g was increased from 3.153 eV for pure ZnO to 3.974 eV for (Fe + Cu) samples (i.e., 0.821 eV more), while it was decreased to 2.851 eV for (Fe + Ni) samples (i.e., 0.302 eV less). A direct behavior is obtained between E_g and both elastic modulus (Y, β), lattice and micro strains (ε_L, ε_m), dislocation density (δ), residual stress (σ) and carrier density N, whereas a reverse behavior is obtained between E_g and both crystallite size (D), porosity (PS) and inter-atomic distance (R). These results are explained in terms of the generated blocked states of the conduction band as indicated by the Burstein Moss effect. These novel findings reveal that the co-doping has intense ZnO and moderate metal oxide modes in the ZnO matrix structure, which makes ZnO co-doped with (Fe + Cu) more suitable for gas sensors and optoelectronic devices. In contrast, ZnO co-doped with (Fe + Ni) samples is strongly recommended for altering plastic deformation. To our knowledge, the present investigation can be considered the first study and probably has never been discussed elsewhere, which highlights the present investigation.