Structural, Thermal and Luminescence Study of Ceria Nanocrystals Dispersed in Silica Matrix
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ORIGINAL PAPER
Structural, Thermal and Luminescence Study of Ceria Nanocrystals Dispersed in Silica Matrix Neelam Rani 1 & Rachna Ahlawat 1
&
Bindiya Goswami 1
Received: 14 March 2019 / Accepted: 6 September 2019 # Springer Nature B.V. 2019
Abstract Ceria (CeO2) nanocrystals dispersed in silica were prepared by sol-gel, a very suitable method for large-scale production. The formation of cubic fluorite structure of CeO2 nanocrystals was confirmed by XRD, TG-DTA and TEM. The average nanocrystalline size has been calculated ~3-5 nm using Debye-Scherrer formula for different annealed samples. The calculated nanocrystalline sizes were compared with W-H plot and TEM histograms. Different structural parameters like microstrain, lattice constant, dislocation density, X-ray density and activation energy were also calculated for all prepared samples. We have examined the photoluminescence (PL) due to defect centers and Ce3+ ions present in prepared nanopowder which were excited at two different wavelengths. PL study revealed the effect of annealing on the emission spectra and resulted that the emission efficiency of direct excitation at λex = 325 nm was enhanced with respect to the indirect λex = 250 nm. The emission produced from CeO2 nanocrystals dispersed in amorphous silica matrix has been influenced by many factors such as the modification of the ligand field around the Ce3+ ions in silica, presence of hydroxyl ions and annealing temperature also. Detailed Energy transfer mechanism has been explained with all possible transition lines. Keywords CeO2 nanocrystals . TEM . PL . Excitation spectra . Emission spectra etc.
1 Introduction Nowadays metal oxides having special size and different morphology are attracted great attention due to their important applications in enormous fields like catalysis, medicine, electronics, ceramics, cosmetics etc. Metal oxides (ROx, where R = Y, Gd, Ce, Zr, Ti, Nd etc) are playing an increasingly important role in solid-state physics, chemistry and materials sciences [1–3]. Ceria (CeO2) with a cubic fluorite-type structure has attracted great deal of interest due to its special properties like UV absorption capacity, good mechanical strength, more stability at elevated temperature, high hardness, large oxygen ion conductivity and oxygen storage capacity [4, 5]. Ceria is also act as potential activators in different solid host lattices i.e. single crystals, polycrystalline ceramics and glassy powders for producing multi-functional materials to be used as phosphors [6], scintillators [7], gas sensors [8] antibactrial * Rachna Ahlawat [email protected] 1
Department of Physics, Materials Science Lab, Chaudhary Devi Lal University, Sirsa 125055, Haryana, India
and antioxidant [9] due to its allowed 5d-4f transitions. A strong overlap of the activator 5d orbitals with ligand orbital causes high sensitivity of their spectral characteristics to the local environment structure. Therefore, the luminescence arising from Ce3+ doped with different glasses is frequently utilized as a ph
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