Optical spectra of Nd3+ in niobates of the tetragonal tungsten bronze family

Nd:Ba-2.NaNb5O15 (Nd:BNN), Nd:Ba2KNb5O15 (Nd:BKN) and Ba-1.Nd-90(0.26) Li0.42Nb5O15 (BNdLN) single crystals with the tetragonal tungsten-bronze (TTB) structure have been grown by means of the 'flux growth' method. The 10 and 298 K absorption and emission spectra and the room temperature decay curves have been measured and discussed in the light of the crystallographic information. The room temperature absorption spectra of Nd:BKN and BNdLN have been analysed in the framework of Judd-Ofelt theory and the Omega(lambda) (lambda = 2, 4, 6) intensity parameters have been evaluated. The structural and emission properties of a new TB phase, Nd:Ba2LiNb5O15 (Nd:BLN), have also been reported because they are useful in the discussion concerning the site occupancy of the active ions in these materials.