Origin of the active luminescence from Sm-activated borate phosphors: a correlational study of trap states and decay kinetics

• Published in: New journal of chemistry 2023-01, Vol.47 (3), p.1472-1478
• Main Authors: Anitha, N, Jayanthi, K, Rakshita, M, Sharma, Aachal A, Jayarambabu, N, Akshaykranth, A, Babu, Kishore, Rao, T. Venkatappa, Dinakar, D, Haranath, D
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d2nj04601f

The photoluminescent (PL) properties of Sm 3+ -doped strontium hexaborate (SrB 6 O 10 ) phosphors are significantly influenced by their crystallinity, phase and dopant concentration. To obtain a high brightness orange-red emitting SrB 6 O 10 :Sm 3+ phosphor, a controlled and modified soluble-salt reaction method in the presence of a chelating agent (citric acid, C 6 H 8 O 7 ) was used at ∼700 °C for about half an hour under an air atmosphere, which is otherwise only possible at very high (>1500 °C) sintering temperatures. The PL spectrum of the SrB 6 O 10 :Sm 3+ phosphor produced strong and intense PL emission peaks centered at 560 nm ( 4 G 5/2 → 6 H 5/2 ), 596 nm ( 4 G 5/2 → 6 H 7/2 ), and 640 nm ( 4 G 5/2 → 6 H 9/2 ) under excitation of 400 nm ( 6 H 5/2 → 6 H 7/2 ). This is one of the very few reports that depicts the formation of more shallow traps in the lattice and the concentration quenching phenomenon was attributed to the non-radiative transfer of energy among Sm 3+ ions via dipole-dipole interactions in the trap states. The optimized phosphor has noticeable reddish-orange Commission International de I'Eclairage color coordinates of (0.459, 0.337). The PL decay kinetics of the synthesized phosphor showed a biexponential decaying characteristic with an overall decay time of milliseconds. The presence of borate ions benefitted the thermal stability of the SrB 6 O 10 :Sm 3+ phosphor as well. X-ray diffraction studies confirmed the phase purity, while scanning electron microscopy revealed the morphology to be an agglomerated rod-like structure. The PL intensity increased with increasing Sm 3+ concentration and reached the optimum at 0.1 mol%. The obtained results clearly indicate that the SrB 6 O 10 :Sm 3+ phosphor is a viable material for providing a red component for white-light emitting diodes (w-LEDs). A series of Sm 3+ -activated strontium hexaborate (SrB 6 O 10 ) red phosphors has been synthesized using a soluble salt reaction (SSR) method and the correlation between their trap states and decay kinetics was studied in detail.