Synthesis, characterization and spectroscopic investigation of Cr3+ doped wollastonite nanophosphor

• We present a facile low temperature method for synthesis of CaSiO3 doped with Cr3+.
• In this method we have obtained phase pure CaSiO3 at 950 °C.
• CaSiO3:Cr3+ red phosphor’s emission properties depend on the concentration of Cr3+.
• Racah parameters to describe electron–electron repulsion effects are studied.
• Relationships between concentration of Cr3+ and PL are firmly established.

This work explores the preparation of nanocrystalline Cr3+ (1–5 mol%) doped CaSiO3 phosphors by solution combustion process and study of its photoluminescence (PL) behavior. The nanopowders are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red (FTIR) spectroscopy. PXRD results confirm monoclinic phase upon calcination at 950 °C for 3 h. SEM micrographs indicates that the powder is highly porous and agglomerated. The TEM images show the powder to consist of spherical shaped particles of size ∼30–60 nm. Upon 323 nm excitation, the emission profile of CaSiO3:Cr3+ exhibits a narrow red emission peak at 641 nm due to 2E → 4A2 transition and broad band at 722 nm due to 4T2g → 4A2g. It is observed that PL intensity increases with increase in Cr3+ concentration and highest PL intensity is observed for 3 mol% doped sample. The PL intensity decreases with further increase in Cr3+ doping. This decrease in PL intensity beyond 3 mol% is ascribed to concentration quenching. Racah parameters are calculated to describe the effects of electron–electron repulsion within the crystal lattice. The parameters show 21% reduction in the Racah parameter of free ion and the complex, indicating the moderate nephelauxetic effect in the lattice.

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