Blue light emitting Eu doped Ca2P2O7 and Ba2P2O7 particles synthesized at low temperatures

beta-Ca2P2O7 and s-Ba2P2O7 doped with Eu3+ ions were prepared by annealing the precursor materials, CaHPO4: Eu and BaHPO4: Eu respectively, over the temperature range of 500-800 degrees C. Bright blue emission with colour coordinates (0.17, 0.04) has been achieved from these samples upon heating CaHPO4: Eu/BaHPO4: Eu in Ar medium at 800 degrees C. Blue emission arises due to transition from the excited state 4f(6)5d(1) to ground state S-8(7/2) of Eu2+ in the sample. Carbon produced, due to charring of ethylene glycol moiety present with the precursor material during annealing, facilitates the partial reduction of Eu3+ to Eu2+ in the sample. Large difference in the ionic radii between Eu3+ and Ba2+ ions and associated distortion in the local environment is responsible for the observed difference in the luminescence properties Ca2P2O7: Eu and Ba2P2O7: Eu samples.