A promising orange-red emitting nanocrystalline NaCaBO₃:Sm³⁺ phosphor for solid state lightning

Orange-red emitting NaCaBO3:Sm³⁺ nanophosphors were prepared by combustion method using metal nitrates and urea as initial materials. The phase of the product was identified by x-ray diffraction technique (XRD) and was found to be orthorhombic with a space group Pmmn and lattice parameters a = 16.12 Å, b = 10.25 Å, c = 3.52 Å and V= 581.60 Å3 calculated with the POWD program. The average particle size of the nanophosphor calculated from the XRD data and cross verified by TEM was 34 nm. The spectral properties of the NaCaBO3: Sm³⁺ nanophosphors were studied under near UV and electron excitation, which shows characteristic emission lines assigned to the transition (4G5/2 to the 6Hj, j = 5/2, 7/2, 9/2, 11/2) of the Sm³⁺ ion. The optimal Sm³⁺ ion concentration and its critical energy distance were determined as x = 2 mol% and 59.97 Å, respectively and the dipole-dipole interactions were responsible for concentration quenching in the present phosphor. The band gap of the phosphor was calculated to be 5.82 eV. The phosphorescence decay curve was also measured.