Cathodoluminescence and photoluminescence of BaTa2O6:Sm3+ phosphor depending on the sintering temperature

The effect of sintering temperature on the structural and spectroscopic (CL, PL, decay) properties was investigated using 2.5 mol% Sm3+ doped BaTa2O6 samples, which were fabricated by solid state reaction at temperatures of 1150, 1250, 1350, 1425 degrees C. In XRD analysis of Sm3+ doped BaTa2O6 samples, orthorhombic phase appeared at temperatures of 1150 and 1250 degrees C, later the impurity phases disappeared at 1350 degrees C where orthorhombic polymorph completely transformed into a tetragonal tungsten bronze (TTB) structure. SEM analysis revealed the increase of grain size of Sm3+ doped BaTa2O6 with increasing sintering temperature. PL emissions were observed due to (4)G(5/2) -> H-6(J) (J = 5/2, 7/2, 9/2, 11/2, 13/2) transitions of Sm3+ where the emissions increased with the effect of increasing temperature and reached maximum at 1425 degrees C. The increase of PL emissions can be attributed to the developing of the tetragonal phase crystallinity which led to the decrease of non-radiative centers. CL emission of the undoped sample sintered at 1425 degrees C was monitored by the broad blue peak at about 495 nm which is related with the intrinsic emission of BaTa2O6. CL emissions of the doped samples sintered between 1150 and 1425 degrees C showed the host emissions and characteristic emissions of Sm3+ corresponding to (4)G(5/2) -> H-6(5/2), (4)G(5/2) -> H-6(7/2), (4)G(5/2) -> H-6(9/2), (4)G(5/2) -> H-6(11/2) transitions. The Sm3+ concentration led to a decrease in the decay time and an increase in the energy transfer, while the sintering temperature effect showed a different process where the decay time and energy transfer slightly increased.