Design, synthesis, crystal structure and luminescent properties of a new tantalum-phosphate K3BiTaP3O13 with negligible concentration quenching and good thermostability

Abstract

The luminous efficiency of rare-earth (Ln³⁺)-doped luminescent materials suffers greatly from the negative concentration quenching effect, which can be surmounted by a large separation of Ln³⁺ ions in the host lattice. Herein, this study reports a novel tantalum-phosphate K₃BiTaP₃O₁₃ (KBTP) that possesses a ‘chain-like’ structure when viewed along the c-axis, containing [TaO(PO₄)₂]_∞, K_∞ and [Bi(PO₄)]_∞ chains. UV-Vis spectroscopy and density functional theory (DFT) calculations reveal that K₃BiTaP₃O₁₃ has an indirect band-gap of 3.99 eV, making it suitable as a luminescent host matrix. A series of Eu³⁺ or Tb³⁺ phosphors KBTP:xEu/Tb (x = 0.1–1) were prepared and their fluorescent performance was studied. Due to the Bi³⁺ ions being far apart in the KBTP host, the negative concentration quenching effect of the prepared phosphors was greatly limited, even when the concentration of Eu/Tb reached up to 80% replacing Bi³⁺. Moreover, both phosphors had good heat-resistance properties at 30–200 °C, keeping 85.6% (KBTP:0.8Eu) and 71.3% (KBTP:0.8Tb) of the initial intensity at 200 °C. These results preliminarily suggest that KBTP is promising as a host material for both Eu³⁺ and Tb³⁺ fluorescence.