587 June-(5)- pmd J. Indian Chem. Soc., Vol. 94, June 2017, pp. 587-591 Gamma radiation effect on structure and photoluminescence properties of RE 3+ (Tb 3+ /Ce 3+ ) activated GdPO 4 phosphor Sudheer Gurugubelli a , Vemareddy Bheeram a , Anima S. Dadhich a , Abhijit Saha b and Saratchandra Babu Mukkamala* a a Department of Chemistry, Gitam Institute of Science, GITAM University, Visakhapatnam-530 045, Andhra Pradesh, India b UGC-DAE consortium for Scientific Research, Kolkata-700 098, India E-mail : mscbabu@yahoo.com Manuscript received online 15 February 2017, accepted 23 February 2017 Abstract : RE 3+ (Tb 3+ /Ce 3+ ) activated GdPO 4 phosphor has been synthesized by hydrothermal route at 150 º C using citric acid as chelating agent. The synthesized phosphor has been characterized by TEM, TG/DTA, Pow- der X-ray diffraction and photoluminescence spectra. GdPO 4 displayed green emission after doping with Tb 3+ . The influence of  -radiation on structural and photoluminescence properties of GdPO 4 : Tb 3+ ,Ce 3+ was also examined at 5 and 300 kGy. Quenching of PL intensity was observed in GdPO 4 : Tb 3+ ,Ce 3+ after exposure to  -radiation. Moreover, this phosphors exhibited high structural stability upon  -radiation exposure. Keywords : Gadolinium phosphate, hydrothermal synthesis, photoluminescence,  -radiation. Introduction Rare-earth (RE) doped gadolinium based phosphors have been extensively investigated in recent years due to their unique optical applications such as tunable light-emitting diodes, lasers 1,2 , mercury-free fluores- cent lamps 3 , plasma display panels (PDPs) 4 , solid state lighting, field emission display devices, radiation dosimetery and -ray photography 5,6 . Phosphate based phosphors are widely used when compared to other phosphor materials due to its high chemical stability and ecofriendly characteristics 7,8 . Gadolinium phos- phate (GdPO 4 ) is well known as multifunctional mate- rial with structural diversity among all other rare earth phosphates 9 . Its photoluminescent properties can be tuned by incorporating the rare earth elements into the host 10 . GdPO 4 emits intense green light luminescence after doping Tb 3+ ions as a sequence of transitions 5 D 4 / 7 F j (j = 3, 4, 5 and 6) 11 . The photoluminescence brightness of Tb 3+ doped GdPO 4 is significantly en- hanced by incorporating the co-dopant, cerium (Ce 3+ ) in its host lattice. High energy radiations such as X- rays and X-rays may influence the displacement of atoms from their positions in the crystal lattice de- pending on the energy of ionization radiation 12,13 . Io- nizing radiation due to non-linear interaction of elec- tronic excitations can play an important role in lumi- nescence property of materials 14,15 . Furthermore, GdPO 4 act as promising MRI con- trast agent through enhanced T1 relaxation due to more number of unpaired electrons in its atoms 16 . By incor- porating the rare earth elements into Gd 3+ host lat- tice, the luminescent property and drug carrier capa- city of GdPO 4 are also enhanced 17 . It is well known that, citric acid is used as additive/chelating agent to synthesize the bio-ligand coated and surface modified phosphate based phosphors for biomedical applica- tions 18–21 . This study demonstrate the synthesis, characteriza- tion and properties of citric acid coated GdPO 4 : Tb 3+ and GdPO 4 : Dy 3+ phosphors. The luminescence emis- sions of GdPO 4 : Tb 3+ ,Ce 3+ has been examined un- der ultraviolet excitation. The structural stability of both compounds were tested after exposure to gamma radiation.