A new langbeinite‐type phosphate K 2 GdHf(PO 4 ) 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, K 2 GdHf(PO 4 ) 3 [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single‐crystal X‐ray diffraction. Theoretical studies reveal that K 2 GdHf(PO 4 ) 3 is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O‐2 p →Hf‐5 d transition. A Ce 3+ ‐doped phosphor, K 2 Gd 0.99 Ce 0.01 Hf(PO 4 ) 3 , was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5 d 1 →4 f 1 transition of Ce 3+ . 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 K 2 Gd 0.99 Ce 0.01 Hf(PO 4 ) 3 can be used as a good blue phosphor for three‐colour white‐light‐emitting diodes (WLEDs).