Lanthanum hafnate () or lanthanum hafnium oxide is a mixed oxide of lanthanum and hafnium.
Properties
Lanthanum hafnate is a colorless ceramic material with the La and Hf atoms arranged in a cubic lattice. The arrangement is a disordered fluorite-like structure below , above which it transitions to a pyrochlore phase; an amorphous phase also exists below .
The compound decomposes into its constituent oxides at 18 GPa.
Luminescence
Oxygen vacancies in the base material give luminescence spanning across the visible light spectrum, with a peak near 460 nm. The luminescent properties can be fine-tuned by doping with various rare earth and group 4 metals; for example, nanoparticles exhibit a red photoluminescence or radioluminescence near 612 nm when exposed to ultraviolet or X-ray radiation.
Synthesis
Bulk ceramics can obtained by combusting the elements in powder form, and then pressing and sintering the powder at 180 MPa and for 6 hours: 4 La + 4 Hf + 7 → 2 . It may also be made by precipitating hafnium and lanthanum hydroxides from solution and then calcinating in air at for 3 hours: 2 + 2 → + 7 .