Development of Nd3+-doped monoclinic dimolybdates La2Mo2O9 as optical materials

The work presented is mainly focused on synthesis and study of structural and optical properties of microcrystalline Nd3+-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 Nd3+-doped phases with monoclinic structure (α-form, space group P21, unit cell parameters a = 7.1426, b = 7.1544, c = 7.1618 Aa and β = 89.538 ) were observed for a concentration of the optically active ions equal to 5 %. When the concentration of the Nd3+ ions is higher than 15 %, a cubic structure is formed (β-form, space group P213, with the lattice parameter a = 7.155 ± 0.005 Aa). A series of Nd3+-doped La2Mo2O9 phases with different concentration of Nd3+ were prepared using conventional solid-state reactions. The formation of phase-pure Nd3+-doped La2Mo2O9 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 Nd3+ 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 Nd3+ ions. First results show that this new Nd3+-doped monoclinic La2Mo2O9 molybdate phosphor is promising for applications of ultra-short pulse lasers. (orig.)