Short Communication Assessment of electron-vibrational interaction (EVI) parameters of YAG:Ce 3+ , TAG:Ce 3+ and LuAG:Ce 3+ garnet phosphors by spectrum fitting method Govind B. Nair ⁎, S.J. Dhoble Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033, India abstract article info Article history: Received 17 June 2016 Received in revised form 25 October 2016 Accepted 26 October 2016 Available online 28 October 2016 The electron–vibrational interaction (EVI) in 4f ↔ 5d optical transitions of Ce 3+ ions in YAG, TAG and LuAG garnet phosphors have been analysed in this work. The main EVI parameters that have been estimated and reported here are Huang-Rhys factor, effective phonon energy, Stokes shift, red shift and Zero-phonon line position. The EVI parameters were estimated from the room temperature photoluminescence results that were recently re- ported. The spectrum fitting method was employed to determine the EVI parameters. An emission band was modelled with the aid of the calculated EVI parameters. The agreement between the modelled emission bands with the experimentally obtained ones validated the estimated values of EVI parameters. © 2016 Elsevier B.V. All rights reserved. Keywords: EVI parameters Ce 3+ ions Garnets Modelling 1. Introduction Garnets doped with Ce 3+ ions have shown core charisma in a num- ber of applications such as in scintillators and phosphors. YAG:Ce 3+ is a highly recognized commercial yellow emitting phosphor that is used in white LEDs. On the other hand, LuAG:Ce 3+ phosphor is considered for their excellent properties as scintillators. YAG (Y 3 Al 5 O 12 ), LuAG (Lu 3 Al 5 O 12 ) and TAG (Tb 3 Al 5 O 12 ) belong to a class of garnets having the general formula A 3 B 3 C 2 O 12 , where A denote sites with dodecahedral co-ordination, B represents octahedrally co-ordinated sites and C de- note tetrahedrally co-ordinated sites, respectively [1]. The site A may be occupied by Y 3+ , Lu 3+ or Tb 3+ ions, whereas the sites B and C are oc- cupied by Al 3+ ions in these garnets. These phosphors show cubic struc- tures with Ia 3d symmetry. The site A is surrounded by a framework of AlO 4 tetrahedrons and AlO 6 octahedrons, which are connected with each other by sharing their corner atoms. The positioning of atoms in a host lattice and the bond strength among them influences the photoluminescence spectra of a luminescence centre in that host. The coupling between the atoms can often affect the electron-phonon vibra- tions in a host crystal. It is often essential to obtain a wide understanding of the fundamentals and mechanisms involved in the luminescence pro- cesses taking place in a phosphor material. This vital information could be utilized to enhance the properties of phosphors before considering their use in some lighting device. The study of energy transformation and the non-radiative energy transfer between the excited and ground states in luminescent centres often require the knowledge of EVI pa- rameters [2]. Among the lanthanides, the EVI parameters are generally determined for the 4f-5d transitions of Eu 2+ and Ce 3+ ions using the spectrum fitting method. In case of Ce 3+ and Eu 2+ ions, the 4f n ↔ 4f n - 1 5d transitions are hugely affected by the lattice arrange- ment of the host material in which these ions are doped. Such transi- tions arise when an electron jumps from a 4f shell to an unscreened empty 5d shell accompanying a lattice rearrangement. For such a case, the vibronic coupling is strong and as a result, it becomes essential to have knowledge about the electron-vibrational interaction occurring in such transitions. On the contrary, the EVI parameters are not signifi- cant in case of 4f-4f transitions occurring in other lanthanide ions. The vibronic coupling is very weak for 4f-4f transitions, since the 4f shell is shielded by the completely filled 5s and 5p shells. The vibrational modes contribute to the formation of broad excitation and emission bands. With rising temperature, there is an increase in the lattice vibra- tions and the electron-vibrational interaction becomes more significant. Consequently, we observe the excitation and emission spectra of Ce 3+ and Eu 2+ ions to broaden with rising temperature [3]. The EVI parame- ters have significant effect on the phosphor properties and this is note- worthy while considering the phosphor for potential application in lighting devices. A small Stokes shift results in a high luminescence quenching temperature. A small electron-phonon interaction leads to small value of Huang-Rhys factor. This means that the luminescence will be more stable with varying temperature. In other words, the small- er Huang-Rhys factor is an indication of more thermally stable Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 173 (2017) 822–826 ⁎ Corresponding author. E-mail address: govind1291@yahoo.com (G.B. Nair). http://dx.doi.org/10.1016/j.saa.2016.10.049 1386-1425/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa