Investigation of the cationic distribution within the lattice of a series of niobates with tetragonal tungsten bronze structure

Single Crystals of the series K3Sr2LnNb10O30 (Ln = Lanthanide) have been grown by two different techniques: micro-pulling down and solid state growth. The cationic distribution within the three large cavities of the lattice, determined from the crystal structure resolution, shows that the crystal-chemical formula is depending on the route of preparation. A spectroscopic study has evidenced a broadening of the emission peaks which is also compatible with a disorder distribution of Ln3+ ions over 12- and 15-fold cavities.