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

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, K₂Gd_0.99Ce_0.01Hf(PO₄)₃, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d¹→4f¹ 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 K₂Gd_0.99Ce_0.01Hf(PO₄)₃ can be used as a good blue phosphor for three‐colour white‐light‐emitting diodes (WLEDs).