Synthesis and luminescence studies of novel rare earth activated lanthanum pentaborate

The lanthanum pentaborate (LaB5O9) is a novel material which exhibits excellent luminescence when doped with rare earth ions. It was prepared by a novel technique which is a slight variation of solution combustion synthesis. The synthesis is based on the exothermic reaction between the fuel (urea) and oxidizer (ammonium nitrate). The structure of the prepared material was confirmed by powder XRD technique. The photoluminescence of rare earth ions (Ce3+, Eu3+) and sensitized luminescence of Gd3+(Pr3+ -Gd3+ and Bi3+ -Gd3+) in LaB5O9 have been studied. LaB5O9:Ce3+ shows broad band UV emission at 317 nm and LaB5O9:Eu3+ shows orange red emission. LaB5O9: Pr3+-Gd3+ and LaB5O9: Bi3+-Gd3+ exhibit efficient luminescence of Gd3+ in narrow UVB region at 310 nm. The material (La0.5 Pr0.4)B5O9:Gd0.1 exhibits intense narrow band UVB emission at 310 nm and could be a potential candidate for UVB phosphors used in phototherapy lamps. (author)