Structural and magnetic properties of MnZnO composites synthesized from waste alkaline and Zn/C batteries

MARIA VICTORIA GALLEGOS; CARLA ROMINA LUNA; LAURA C. DAMONTE; JORGTE E. SAMBETH; PAULA V. JASEN

Roma

Congreso; 5th International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM 2018); 2018

The zinc oxide (ZnO) is classified as a transparent semiconductor, with a wideband gap of 3.4 eV and a large exciton binding energy of 60 eV. The ZnO materialwhich crystallizes in the wurtzita structure is piezoelectric material. This material can be obtained with a variety of techniques such as vapor phase transport, chemical vapor deposition and sputtering. Each technique used involve different growth mechanisms resulting in bulk crystals with defects or/and impurity background,which affect the electrical and optical properties of bulk. Native or intrinsic point defects -such as vacancies, interstitials and antisites- have long been believed to play a central and even more important role in ZnO. In the other hand,p-type doping of ZnO has attracted considerable attention due to its potential in several areas as optoelectronic devices. Particularly, Mn-doped ZnO has attracted interest in the last years since Mn is incorporated substitutionally at the Zn site. The present work studies the properties of Mn-doped ZnO, and the effect in some chemical and physical properties when charged oxygen vacancy (VOq) are present in the bulk system. First-principles calculations based on Density Functional Theory (DFT), implemented in the Vienna Ab initio Simulation Package (VASP) code is used. Moreover, for improve the results for Zn and Mn species the Hubbard modelis taken account.The results shown that the ZnO bulk has non-magnetic behavior; but the substitution of one Zn for one Mn atom leads to an increase of magnetic moment from 0.00 μB to 4.39 μB per atom. This value is close to the value of 5.0 μB predicted for purely ionic Mn2+ with five unpaired 3d electrons, corresponding to a ferromagnetic state. Regarding to the semiconductor behaviour, the obtained results exhibit that the semiconductor nature still remains with Mn incorporation, leading to a band gap (Eg) reduction of 70 % respect to ZnO bulk, from 1.76 eV to 0.64 eV. The reduction in Eg arises from the new states that are induced in the forbidden zone due to the Mn d-electrons. These facts do the system Mn-doped ZnO a promising candidate for designing the first ferromagnetic piezoelectric material.