Development of Nd~(3+)-doped Monoclinic Dimolybdates La_2Mo_2O_9 as Optical Materials

摘要

The work presented is mainly focused on synthesis and study of structural and optical properties of microcrystalline Nd~(3+) -doped monoclinic dilanthanum dimolybdate at both room and cyrogenic temperatures (4 K and 77 K). These compounds might be useful for application in the future as optical materials and also as transparent ceramics when the structure is cubic. The Nd~(3+)-doped phases with monoclinic structure (α-form, space group P2_1, unit cell parameters a = 7.1426, b = 7.1544, c = 7.1618 ? and β = 89.538°) were observed for a concentration of the optically active ions equal to 5%. When the concentration of the Nd~(3+) ions is higher than 15 %, a cubic structure is formed (β-form, space group P2_13, with the lattice parameter a = 7.155 ± 0.005 ?). A series of Nd~(3+)-doped La_2Mo_2O_9 phases with different concentration of Nd~(3+) were prepared using conventional solid-state reactions. The formation of phase-pure Nd~(3+)-doped La_2Mo_2O_9 has been monitored by powder X-ray diffraction, DSC, SEM, Raman, and FT-IR absorption techniques. High-resolution absorption and emission spectra, as well as the dynamics of the Nd~(3+) excited states characterized by decay time measurements were recorded from room temperature to 4 K. At least two slightly different crystallographic sites are available for the Nd~(3+) ions. First results show that this new Nd~(3+) -doped monoclinic La_2Mo_2O_9 molybdate phosphor is promising for applications of ultra-short pulse lasers.