Low temperature sol-gel based erbium doped mullite nanoparticles: Structural and optical properties

•Crack-free mesoporous material for optical device is reported by sol-gel method.•Mullite and Er3+ doped mullite grain size within range of 167-202 nm and 40-110 nm respectively is reported.•Refractive index of 1.46 for mullite and 2.7 for Er3+ doped mullite matrix with high transparency is obtained.•Thermally stable, photoluminescent Er3+ doped mullite is beneficial for optical applications at room temperature.

Thermally stable aluminum-silicate i.e. mullite is doped with erbium for optical device applications. The matrix is synthesized and doped with 0.1 M of Er3+ by the sol-gel precursor method at room temperature. Crack-free and uniform distribution of the species was detected and profile of the various elements showed stoichiometric ratios, thus suggesting a homogeneous dispersion of the rare-earth ions inside the heterogeneous mullite host matrix. Different sizes of mullite grains 167-202 nm are observed by FESEM; the addition of erbium gets smaller size of mullite crystals 40-110 nm. The crystallization process is evaluated by X-ray diffraction (XRD) whereas Fourier Transmission Infrared Spectroscopy (FTIR) is used to monitor the bonding of crystalline phases. Average crystallite size in mullite matrix is calculated to be 35.50 nm, whereas smaller crystallite sizes 21.38 nm are observed in the case of doped sample. Brunauett-Emmett-Teller (BET) analysis shows the lower surface area value of doped matrix to be 20 m2/g, pore size of 0.03 nm and pore volume of 0.33 cm3/g. Thermally stable, transparent, high refractive index, photoluminescent Er3+ doped mullite matrix is beneficial for optical applications at room temperature.

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