Optical properties of heat-treated hierarchical structure of Eu3+ modified C-CaIn2O4 of small core–shell crystallites

Abstract

A natural aloe-vera gel is promptly bridging the Eu3+, Ca2+ and In3+ species in a bio-complex of a polymer network, so as it yields a sample Eu3+:CaIn2O4 of small crystallites bonding over a grafted C-sp2 surface layer when it is burnt in a self-propagating combustion in air. The Eu3+ doped C-CaIn2O4 sample appears in a core–shell structure in part of the carbon forming a conjoint surface layer (shell) thereon of the individual crystallites in a hybrid nanostructure. The results are analyzed in terms of XRD patterns, phonon bands (in IR and Raman spectra), XPS bands, and hierarchical microstructure in the samples prepared with different Eu3+ dosages in finely tuning the microstructure and optical properties as useful for an efficient phosphor, optical display system, visible lasers, energy-converters, photocatalysts, optical imaging, medical tools, and several others. A partial Eu3+ → In3+ doping in a crystal lattice CaIn2O4 clearly reflects in a marked expansion of the lattice, as much as 2.2% found in the Eu3+ content progressively raised to 2.0 mol% in a tailored hybrid composite structure. An inbuilt C-sp2 shell structure of the crystallites is characterized in terms of its characteristic phonon bands in a conjoint polymer network, which are accounted well in modified XPS bands in the surface species.