Specific role of Al in the synthesis of electrospun Al:ZnO nanofibers: Thermal and elemental analysis

Abstract

In this contribution, the thermal behavior and elemental analysis of a series of transparent conductive layer based on pure and Al doped ZnO nanofiber samples produced by the electrospinning method was studied. The nanofibers are spun from a PVA based solution where we added zinc acetate and doped by 1, 2, 3, and 4 wt% aluminum acetate. First, we carried out a qualitative study of nanofibers electro-spun on a glass substrate before and after annealing by scanning electronic microscopy (SEM). For all samples, these images show the quality of the deposited nanofibers and the good crystallization for the ZnO one after annealing. The decomposition of ZnO-Al (AZO) fibers after annealing is noticed and discussed justifying the quantitative analysis made in the rest of this work using the coupled techniques of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) performed under air atmosphere. We observe changes in the mass loss process with temperature between the various samples, explained by the role of each compound, i.e. PVA, Zn and Al. This study particularly shows the influence of zinc and aluminum doping in the production of nanofibers by electrospinning for high-performance transparent conductive layers. To validate the results obtained by thermal analysis, complementary study of elemental composition by fluorescent X-ray (XRF) was performed to check the initial composition of the fibers before any heat treatment. Finally, results obtained by inductively coupled plasma spectroscopy show that as soon as Al is added to the initial solution, the elements precipitate out due to the neutral pH of this solution. Consequently, new prospects for the deposition of Al-doped ZnO nanofibers by electrospinning can be envisaged by modifying the acidity of the initial solutions.