Low-temperature synthesis and luminescent properties of lanthanum metaphosphate LaP<sub>3</sub>O<sub>9</sub> : Tb

Promising for inorganic luminophores, terbium-doped lanthanum metaphosphates La1-xTbxP3O9 (x = 0.05, 0.1, 0.2, 0.3, 0.4) were synthesised by extraction-pyrolytic method at low temperature in comparison with known methods. The crystal structure and optical properties of the obtained samples were characterised by X-ray phase analysis, IR and luminescence spectroscopy, and the unit cell parameters were calculated. Сompounds having rhombic structure, pr. gr. C 222 1, were obtained in the temperature range of 500–900°C. All parameters of the unit cell decrease linearly with the introduction of terbium into lanthanum metaphosphate. La1-xTbxP3O9 compounds show intense luminescence in the region of 450–650 nm. The La0.8Tb0.2P3O9 sample obtained in one hour annealing at pyrolysis temperature of 900°C shows maximum luminescence intensity.