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

Abstract

Nd:Ba 2 NaNb 5 O 15 (Nd:BNN), Nd:Ba 2 KNb 5 O 15 (Nd:BKN) and Ba 1.90 Nd 0.26 Li 0.42 Nb 5 O 15 (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 λ (λ = 2, 4, 6) intensity parameters have been evaluated. The structural and emission properties of a new TB phase, Nd:Ba 2 LiNb 5 O 15 (Nd:BLN), have also been reported because they are useful in the discussion concerning the site occupancy of the active ions in these materials.

Flux growth, structural studies and spectroscopy of K2NdNb5O15 and Nd:K2LaNb5O15 crystals

“…The refinement of the sites occupancies indicates that the K + cations are located at the A 1 sites and the La 3+ or Nd 3+ ones at the A 2 sites, even if the presence of a spectroscopically detectable amount of optically active centers in the pentagonal A 1 sites cannot be excluded in the case of KNdN. As in previously studied cases [3] a structural modulation is present as a consequence of the cooperative tilting of the NbO 6 units along given directions. This aspect will be discussed in detail in a future paper: in this context it is sufficient to point out that such a modulation implies distortions of the coordination polyhedra and then inhomogeneities in the crystal field surrounding the optically active ions.…”

“…The experimental setup used for the structural characterization has already been described in a previous paper [3]. The absorption and emission spectra were measured using a SPEX spectroscopic system equipped with a 1.26 m monochromator, suitable to ensure a spectral resolution of 0.1 nm in the considered wavelengths range (see Refs.…”

“…The absorption and emission spectra were measured using a SPEX spectroscopic system equipped with a 1.26 m monochromator, suitable to ensure a spectral resolution of 0.1 nm in the considered wavelengths range (see Refs. [3,4] for more details).…”

“…Ba 2 NaNb 5 O 15 (BNN) for example, is a frequency doubler crystal that can be activated with rare earth ions to yield attractive solid state laser materials [1,2]. We have developed a flux growth method for the synthesis of rare earth-doped TTB niobates in form of single crystals suitable for structural and spectroscopic studies which have provided new information about these materials and their perspectives of application [3,4]. In this paper we present some preliminary results of our investigations on K 2 NdNb 5 O 15 (KNdN) and 1% Nd 3+ -doped K 2 LaNb 5 O 15 (Nd:KLaN) crystals.…”

Luminescence properties of Ba2NaNb5O15 crystals activated with Sm3+, Eu3+, Tb3+ or Dy3+ ions

“…Crystals with size up to of 2 Â 2 Â 3 mm 3 were separated from the flux by dissolving it in hot diluted HCl. BNN is tetragonal and belongs to the P4bm space group, with cell parameters a= 12.463 and c= 3.990Å and Z =2 [8]. Its structure (Fig.…”