Influence of crystal field potential on the spectroscopic parameters of SiO 2  B 2 O 3  PbO glass doped with Nd 2 O 3 N.O. Dantas a , E.O. Serqueira a , M.J.V. Bell b,n , V. Anjos b , E.A. Carvalho b , S.A. Lourenc - o c , M.A. Pereira-da-Silva d,e a Laborato ´rio de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Fı ´sica, Universidade Federal de Uberlˆ andia, CP593, 38400-902, Uberlˆ andia—MG, Brazil b Laborato ´rio de Espectroscopia de Materiais, Departamento de Fı ´sica, Universidade Federal de Juiz de Fora, Juiz de Fora-MG, 36036-330, Brazil c Universidade Tecnolo ´gica Federal do Parana ´—Campus Apucarana, 86812-460, Apucarana—PR, Brazil d Instituto de Fı ´sica de S ~ ao Carlos, USP, S ~ ao Carlos, SP 13560-250, Brazil e Centro Universita ´rio Central Paulista, UNICEP, S ~ ao Carlos, SP 13563-470, Brazil article info Article history: Received 13 October 2010 Received in revised form 2 January 2011 Accepted 24 January 2011 Available online 4 February 2011 Keywords: Glasses Nanoparticles Raman Luminescence Nd 3+ Judd–Ofelt theory abstract This paper presents the optical characteristics of Nd 3+ silicate glass (SiO 2 –B 2 O 3 –PbO), synthesized by the fusion method. Two sets of samples were prepared: glass and corresponding glass ceramics. Optical absorption, luminescence, Raman spectroscopy and atomic force microscopy (AFM) measurements were performed in order to determine the structural properties of the systems and the radiative characteristics of Nd 3+ ions. Near infrared luminescence exhibited typical Nd 3+ bands. Raman and AFM measurements indicated nanocrystal growth with thermal treatment of the glass ceramics. Judd–Ofelt calculations also confirmed that heat treatment induced structural rearrangement of the samples that was dependent on Nd 2 O 3 concentration. This resulted in changes in the optical and physical properties of the samples, including stimulated emission cross section and rigidity. & 2011 Elsevier B.V. All rights reserved. 1. Introduction The optical properties of rare-earth-doped dielectric solids have been extensively investigated [1–4]. In particular, the use of rare-earth (RE) ions emitting in the optical-fiber spectral range has attracted considerable interest in luminescent material appli- cations [5,6]. Due to their potential applications in efficient lasing and frequency upconversion processes, the investigation of opti- mized doped systems merits substantial effort. In this respect, one successful approach is to obtain glass ceramics by controlled heat treatment of glass precursors. It has been demonstrated that this procedure improves the mechanical, thermal, electrical and optical properties of a system. In this way, glass ceramics combine the mechanical and optical properties of glass with the crystal- like environment of rare earth ions. The composite material allows control of the chemical environment of the RE ion and reduces clustering and consequent luminescence quenching. SiO 2 –B 2 O 3 –PbO (SBP) glasses present high transparence in the optical window, including the NIR region. In addition, the phonon energy is relatively low due to the presence of high atomic mass elements such as Pb. Phonons play a very important role in Nd- doped glasses, since the higher the phonon energy, the lower the radiative emission. In this sense, the glass composition is eval- uated considering the phonon energies of the components [7]. This paper reports on the optical properties of Nd 3+ ions in SBP glass and glass ceramics. Atomic force microscopy and Raman scattering measurements demonstrated that thermal annealing induced structural rearrangement of the samples, which modified the radiative properties of Nd 3+ . These results were reinforced by Judd–Ofelt calculations. The Judd–Ofelt (JO) theory [8,9] has been widely used to study the environment surrounding RE ions in glass [10–15]. The theory gives the Judd–Ofelt parameters O 2 , O 4 and O 6 , from which radiative properties can be obtained. O 2 is related to the RE  O ligand field asymmetry of the host matrix such that as O 2 increases, symmetry decreases and covalency increases [16,17]. O 6 represents the degree of Ln  O covalency such that decreases in O 6 are associated with high covalency. O 4 is related to ‘‘long range’’ structural interaction like viscosity at high temperatures and ionic packing density at low temperatures [12,13]. 2. Theory The Judd–Ofelt theory [8,9] was used to calculate the radiative rates of Nd 3+ ions in the SBP host in the near infrared spectral Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2011.01.017 n Corresponding author. E-mail address: mjbell@fisica.ufjf.br (M.J.V. Bell). Journal of Luminescence 131 (2011) 1029–1036