Effect of Synthesis Techniques on the Optical Propertiesof Ho3+/Yb3+ Co-doped YVO4 Phosphor:A Comparative Study

摘要

The Ho³⁺/Yb³⁺-codoped YVO4 phosphors have been synthesized by three different techniques (viz., solution combustion, sol–gel, and solid-state reaction techniques). X-ray diffraction patterns confirm the formation of a pure phase in the samples synthesized by all of the three methods; however, the average crystallite sizes in the three cases are different. The crystallite size increases if they are heated to higher temperature. The particle sizes are measured by scanning electron microscopy, which shows an increase in particle size with increasing the calcination temperature. The vibrational behavior of all of the three synthesized phosphor samples is studied by the Fourier transform infrared (FTIR) technique. The UV–vis absorption measurements give a large number of bands in all of the three samples prepared by three different methods. The upconversion (UC) emissions in all three samples have been monitored using a 980 nm diode laser. It gives an intense red emission in all of the three samples. Upconversion emission intensity is more prominent in the phosphor sample synthesized by the sol–gel techniqueand heated at 1473 K. The enhancement in UC emission intensity iswell understood by the shape and size of the particles and also confirmedby the FTIR and UV–vis measurements. It is interesting to notethat whereas UC measurements give red and weak green emissions, downshifting(DS) measurements show intense green, weak red, and broad blue emissionson UV excitation (323 nm). The DS behavior shows the same characteristicsof the enhancement in overall emission. Overall, the phosphor samplesynthesized by the sol–gel method gives better results in upconversionand downshifting behaviors when heated at 1473 K.