Synthesis, structure and photoluminescence properties of Ho3+ doped TTB–BaTa2O6 phosphors

• BaTa2O6 allowed high doping levels of Ho3+ ions due to TTB type structure.
• For charge balance the formula “Ba5−760x/781Ho2xTa10−487x/600O30” may be suggested up to 10 mol% Ho3+.
• Tantalates could be the source of strong CT absorptions where BaTa2O6 act as antennas for RE3+ ions.
• BaTa2O6:Ho3+ phosphor exhibited strong green emission at the transition of 5F4 → 5I8 (546.9 nm).

Ho3+ doped TTB–BaTa2O6 phosphors were produced by the solid state reaction method. XRD analysis confirmed the formation of BaTa2O6 single phase which was accomplished by heat treatment at 1425 °C for 20 h. The crystal structure of TTB–BaTa2O6 allowed doping concentration of Ho3+ ions up to 10 mol%, maintaining a single phase composition. A second phase of HoTaO4 begins to appear at 15 mol%. The lattice structure and the crystallite sizes changed with the concentration of Ho3+. In SEM analysis, it was also shown that BaTa2O6 grain sizes changed with the concentration of Ho3+. EDS analysis revealed that the Ta/Ba ratio increased on the grains depending on Ho3+ concentration. Charge balance of the structure was formulated through the EDS results. In fluorometer analysis, a strong green emission (λem = 546.9 nm) was observed in the visible spectral region. The emission increased with the doping concentration of up to 2.5 mol%, and above this level decreased due to concentration quenching.

Emission spectra of BaTa2O6:Ho3+ phosphors at λex = 451 nm and SEM micrograph for 2.5 mol% doped Ho3+.Figure optionsDownload as PowerPoint slide