Morphology, Structure and Nonstoichiometry of ZnCr2O4 Nanophased Powder

Abstract

It is well established that gas/humidity-sensing properties of spinels are markedly influenced by their stoichiometry and microstructure. In this work nucleation and spinel phase development in the Zn-Cr-O system were investigated from the viewpoint of structural and morphological phenomena occurred during nanophased particle synthesis through aerosol reaction. The aerosol was generated from nitrates precursor solution using ultrasonic atomizer operated at 1.7 MHz. The influence of different decomposition schedules on the particle chemical content and morphology was determined by adjusting the processing parameters (aerosol droplet density 3.9x10 6 droplets/cm 3 , droplet velocity 0.035m/s, max. temperature 900 o C and residence times 3, 6 and 9s). A composite particle structure comprised of primary crystallites sized from 22 to 44nm is revealed by SEM and TEM analysis. XRD structural analysis (crystallite size, microstrains, unit cell and ionic occupancies) is performed in accordance with procedure based on Koalariet-Xfit program. A certain degree of non-stochiometry is characteristic for all powders. Homogenous distribution of the constituting elements and Zn/Cr ratio of about 0.68 are proved by EDAX

Fabrication of nanospinel ZnCr2O4 using sol–gel method and its application on removal of azo dye from aqueous solution

“…The particle sizes of ZnCr 2 O 4 nanoparticles calcinated at 450 and 700 • C are 13 and 40 nm, respectively. The peak intensity of the diffraction peaks and crystalline size increases with increasing the calcination temperature [20].…”

Isobutanol Synthesis from Syngas over Zn‐Cr Catalyst: Effect of Zn/Cr Element Ratio

“…No K 2 O (JCPDS card 47–1701) or K 2 CO 3 (JCPDS card 49–1093) peaks were found, possibly because the small amount of potassium species were highly divided over the catalysts surfaces. The main diffraction peaks are consistent with Cr 2 O 3 and Zn−Cr spinel in XRD pattern of Zn 1 Cr 3 catalyst . As increasing the Zn/Cr element ratio to 1 : 1, the Zn 1 Cr 1 catalyst just presented nonstoichiometric spinel phase .…”

“…The main diffraction peaks are consistent with Cr 2 O 3 and ZnÀ Cr spinel in XRD pattern of Zn 1 Cr 3 catalyst. [18][19][20] As increasing the Zn/Cr element ratio to 1 : 1, the Zn 1 Cr 1 catalyst just presented nonstoichiometric spinel phase. [20] The reflections of ZnO phase appeared and became sharper with Zn/Cr element ratio further increasing to 3 : 1 (Zn 3 Cr 1 catalyst) and 5 : 1 (Zn 5 Cr 1 catalyst), suggesting that the particle size of ZnO was becoming larger.…”

Phase Transformation and Optical Properties of Annealed Hydrothermally Synthesized ZnO/ZnCr2O4 Nanocomposites

“…Ternary semiconductors, having spinel structure and general formula of AB 2 O 4 where (A = Zn, Mg Cu, Ge, B = Cr, Al, Co, Ga or In), are some of the most studied compounds in solid‐state devices due to their wide range of applications, viz. humidity sensing, photocatalysis, gas sensing, and optoelectronic applications . In particular, ZnCr 2 O 4 is one of the best example of ternary semiconductors with spinel structure has attracted many attention of scientific community due to its high thermodynamic stability and unique sensing properties .…”

“…humidity sensing, photocatalysis, gas sensing, and optoelectronic applications. [6][7][8][9] In particular, ZnCr 2 O 4 is one of the best example of ternary semiconductors with spinel structure has attracted many attention of scientific community due to its high thermodynamic stability and unique sensing properties. 4,6 In recent past, ZnO-and ZnCr 2 O 4 -based nanostructure has been synthesized by various techniques such as, chemical vapor deposition, wet chemical bath deposition, spray pyrolysis, metal-organic chemical vapor deposition, sol-gel, pulsed laser deposition, [10][11][12][13][14][15][16][17][18] high-temperature solid-state reaction, 19 and hydrothermal techniques.…”