Thermal behavior of precursors for synthesis of Y2SiO5:Ce phosphor via gel combustion

Abstract

Different types of precursors were prepared by gel combustion starting from yttrium–cerium nitrate, TEOS, and different fuels (i.e., threonine, arginine, citric acid, and glycine). The precursors were fired at 1400 C in nitrogen or air atmosphere in order to obtain cerium-activated (Y2SiO5:Ce) phosphors with X2-monoclinic structure. The processes involved during the heating of precursors were put in evidence using thermal analysis investigations (TG–DTG–DTA). Correlation between the thermal decomposition steps, mass loss, and composition of evolved gases during the thermal treatment was established using TG/DTA–FT-IR coupling. Precursors prepared with threonine, arginine, and glycine have a similar thermal behavior with a mass loss up to 10.0 %, due to the decomposition of hydrated carbonates. Unreacted nitrate compounds or organic residues have been identified when combustion occurs in fuel-lean (\0.79 mol threonine) or in fuel-rich conditions ([0.79 mol threonine), respectively. Citric acid forms citrate-based compounds during gelation process with inhibitory effect on the combustion process. The conversion to well-crystallized silicates was revealed by changes of FT-IR vibration bands and confirmed by XRD measurements. A blue emission with variable intensities was observed for all phosphor samples depending on the amount and fuel type. Combustion with threonine leads to phosphors with highest luminescent characteristics.