Optimization of dispersed LaPO4:Tb nanosol and their photoluminescence properties

Abstract LaPO4:Tb nanophosphor with different concentrations of Tb3+ 0.05–0.15 mol % has been synthesized via sol-gel process. The synthesized nanophosphor was dried under 80 °C for 24 hrs. Dependent on the different concentration of Tb3+, the optimum concentration for the enhanced luminescence intensity was determined to be 0.15 mol %. The high luminescent nanophosphor with Tb3+ = 0.15 mol % was heat treated at 200–800 °C for 4 hrs. The nanophosphor heat-treated at 600–800 °C showed high photoluminescence (PL) property by monitoring at 254 nm excitation wavelength. The nanophosphor heat-treated at 200–400 °C is well crystalline in the hexagonal phase, but the crystal phase nature is shifted to monoclinic in case of the sample that heat treated above 400 °C. On the basis of weakly agglomerated nanoparticles, the nanophosphor was dispersed and converted into nanosol under controlled bead mill wet process. Based on particle size analyzer (PSA) the obtained nanosol median particle size (D50) was below 200 nm. Finally, the low PL properties of LaPO4:Tb nanosol with their characteristics green color emission was recovered after calcination at 650 °C under N2 atmosphere for 2 hrs. The crystallinity, morphology and particle size of the nanophosphors were investigated using X-ray diffraction (XRD), FE-SEM, and PSA. The nanosol with green color emission prepared in this work potentially meets their applications for security coatings.