A new langbeinite-type phosphate K₂GdHf(PO₄)₃: synthesis, crystal structure, band structure and luminescence properties

Abstract

Langbeinite-type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite-type compound, K2GdHf(PO4)3 [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single-crystal X-ray diffraction. Theoretical studies reveal that K2GdHf(PO4)3 is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O-2p→Hf-5d transition. A Ce3+-doped phosphor, K2Gd0.99Ce0.01Hf(PO4)3, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d 1→4f 1 transition of Ce3+. The average luminescence lifetime was calculated to be 5.437 µs and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K2Gd0.99Ce0.01Hf(PO4)3 can be used as a good blue phosphor for three-colour white-light-emitting diodes (WLEDs).

Polymorphism, polytypism and modular aspect of compounds with the general formula A 2 M 3(TO4)4 (A = Na, Rb, Cs, Ca; M = Mg, Mn, Fe3+, Cu2+; T = S6+, P5+): order–disorder, topological description and DFT calculations

“…Alkaline sulfates and phosphates of alkaline-earth and transition elements attract interest because of electrochemical properties and their application as electrode materials for lithium-and sodium-ion batteries (Hwang et al, 2017;Reynaud et al, 2014;Masquelier & Croguennec, 2013). Moreover, these compounds are also characterized by the luminescent (Sinusaite et al, 2021;Majgier et al, 2021;Nan et al, 2020) and nonlinear optical (Xu et al, 2021;Rajeswari et al, 2018;Joice Malini et al, 2021;Dang et al, 2021;Bai et al, 2021;Marimuthu & Perumal, 2021), magnetic (Kovrugin et al, 2019;Li et al, 2020;Bolotina et al, 2019;Benhsina et al, 2021;Maspoch et al, 2007) and catalytical (Moffat, 1978) properties.…”