Synthesis and characterization of nanosized zinc aluminate spinel from a novel Zn–Al layered double hydroxide precursor

In this paper, a novel Zn–Al layered double hydroxide (LDH) with composition [ZnAl2(OH)6]CO3·nH2O was prepared using the urea method. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed its layered crystalline structure. Nanosized zinc aluminate spinel was successfully synthesized by calcining [ZnAl2(OH)6]CO3·nH2O at the temperatures 700 °C or above. The formation of ZnAl2O4 was monitored via XRD, Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TG-DTA). The optical and textural properties of the Zn–Al LDH and its calcined products were studied via UV–vis diffuse reflection spectroscopy and nitrogen sorption analysis. The band gap value of the sample calcined at 900 °C is in the range of 3.8–4.0 eV and the specific surface area decreases with increasing calcination temperatures.

Graphical abstractSchematic illustration of the experimental procedure for the synthesis of [ZnAl2(OH)6]CO3·nH2O and the conversion of the ZnAl2–CO3-LDH to zinc aluminate spinel by calcination.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel LDH with composition [ZnAl2(OH)6]CO3·nH2O was prepared using urea method. ► Pure ZnAl2O4 spinel is obtained directly from calcination of ZnAl2–CO3-LDH. ► The ZnAl2O4 nanoparticles were of high crystallinity. ► The specific surface area of ZnAl2O4 decreases with increasing calcine temperatures. ► A facile, cheap and green approach is provided for synthesis of ZnAl2O4.