Structural ordering studies of Nd 3+ ion in eulytite-type M 3 Y(PO 4 ) 3 (M=Sr 2+ or Ba 2+ ) phosphates. First translucent ceramics from micro-crystalline cubic powders

Cubic phosphates of M 3 Y(PO 4 ) 3 (M = Sr 2+ or Ba 2+ ) from the eulytite family were studied as potential candidates for new optical polycrystalline ceramics showing transparency. Two series of Nd 3+ -doped Ba 3 Y(PO 4 ) 3 and Sr 3 Y(PO 4 ) 3 micro-powders were synthesized via solid-state reaction method. The correlation between their structure and spectroscopic properties and the effect of divalent Sr 2+ /Ba 2+ cation creating a network was analyzed in detail. The crystal structure of Ba 3 Y(PO 4 ) 3 and Sr 3 Y(PO 4 ) 3 was solved ab initio based on their single crystals. Y 3+ and Sr 2+ /Ba 2+ ions do not share the same symmetry site and some slight distortion over crystallographic positions occupied by divalent and trivalent ions in the cationic sublattice was visible. Nd 3+ reside at the Y 3+ site but partial substitution of Ba 2+ or Sr 2+ cannot be excluded. The cationic and anionic disorder is reflected in spectroscopic properties. Nd 3+ ion used as a structural probe shows multisite character and inhomogeneous distribution in both types of material, as determined using absorption spectroscopy at 4.2 K and laser-excited site-selective luminescence spectroscopy at 77 K. This is also clearly seen in excited state dynamics of 4 F 3/2 doublet analysis. A greater order for barium host lattice was observed. Also, the first un-doped translucent ceramics were obtained from micro-crystalline powders.