Impact of annealing on optimization of various thermal, structural, and optical parameters of spinel ‘gahnite’ for device fabrication

Abstract

The spinel ZnAl2O4 nanopowder has been prepared using the well-known citrate sol-gel technique in which citric acid act as an agent for chelation. The XRD examined the sample crystallinity and phase purity of the samples after annealing at subsequent temperatures. Corresponding functional groups were identified by FTIR. The Surface texture of the samples was interpreted by FE-SEM and HR-TEM, while the constituent elements were evaluated by EDS spectroscopy. The UV-DR spectroscopy exhibits that the bandgap can significantly be tailored in annealed samples owing to the intrinsic impurity energy levels. PL has demonstrated the shift in emission spectra using the site-selective direct and indirect excitations. The prominent emission in the visible region is further emphasized by CIE chromaticity graphs and their specific color coordinates. The decay analysis reveals that the spinel ‘Gahnite’ samples have higher decay constant when excited with direct bandgap energy. It is suggested that the ZnAl2O4 would be a promising substitute as a blue-emitting phosphor in modern photonics.

Insight into the crystalline structure, morphology, luminescence, and electrical conductivity of ZnAl2O4:xMn2+ (0 ≤ x ≤ 2.0 mol%) nanostructures

“…Histograms generally represent the range of nanoparticles versus their occurrence percentage in the form of a bar graph [19]. The undoped ZnAl 2 O 4 sample has a size range of 20-40 nm and most particles were centered at 30 nm, as reported in our earlier publication [20]. While in Mn 2+ doped ZnAl 2 O 4 sample, the range is 15-20 nm and particles are centered around 17 nm as depicted in the histogram.…”

“…With three carboxylic acid moieties, it behaves as a weak tricrotic acid. The detailed synthesis mechanism has been reported in our earlier publications [19,20]. The prepared samples are designated N1, N2 N3 & N4 corresponding to the content of magnesium ion (Mn 2+ ) as 0.5, 1.0, 1.5, and 2.0 mol%, respectively.…”

“…The XRD patterns for ZnAl 2 O 4 : x Mn 2+ (x = 0.0, 0.5, 1.0, 1.5, & 2.0 mol%) spinel nanostructures prepared by the citrate sol-gel method are shown in figure 1 222), (400), (331), (422), (511), (440), (620), (533) reflection planes which can be assigned to the cubic spinel structure with Fd3m ¯space group [20]. The obtained data of the XRD study is well matched with JCPDS No.…”

“…In W-H analysis, the variation occurs as tanθ rather than 1/cosθ as in case of Scherrer equation (1). In any crystalline structure, the difference of 2θ values predicts the changes in peak broadening either contributed by particle size or by induced microstrain [19,20]. The micro-stain (ε) is supposed to be uniform in all crystallographic direction and define by following equation:…”

“…The citrate sol-gel approaches are free from all the above-mentioned drawbacks of the conventional methods and generate nanomaterials with enhanced features [19]. The sol-gel route allows certain chemical reactions that finally stabilize several parameters to modify the operating characteristics of the final product, decrease the synthesis time, and consequently reduce the overall energy [20]. Based on the calculated results of nanostructures, a conceivable way of synthesizing highly dense, pure, with optical sound quality, and constricted band gap Mn 2+ doped ZnAl 2 O 4 nanostructures has been explored.…”