Improved luminescence from Y 2 Sn 2 O 7 :Tb 3+ nanoparticles co-doped with Sb 3+ ions Sandeep Nigam, V. Sudarsan ⇑ , R.K. Vatsa Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India article info Article history: Received 20 May 2010 Received in revised form 8 October 2010 Accepted 2 November 2010 Available online 3 December 2010 Keywords: Y 2 Sn 2 O 7 Luminescence Tb 3+ Sb 3+ abstract Very small nanoparticles (size 3–5 nm) of Y 2 Sn 2 O 7 ,Y 2 Sn 2 O 7 :Tb 3+ and Sb 3+ co-doped Y 2 Sn 2 O 7 :Tb 3+ were prepared at a relatively low temperature of 700 °C. Y 2 Sn 2 O 7 host is characterised by an emission around 436 nm, which is arising from the oxygen vacancies present in the lattice. Tb 3+ emission improves signif- icantly when Sb 3+ ions are co-doped with Y 2 Sn 2 O 7 :Tb 3+ nanoparticles. Incorporation of Sb 3+ ions at the Y 3+ site of Y 2 Sn 2 O 7 lattice and associated lattice distortion around Tb 3+ /Y 3+ ions brought about by the dif- ference in the stable coordination number of Sb 3+ and Y 3+ ions are responsible for the improved Tb 3+ emission from the co-doped samples. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Oxides with pyrochlore structure (A 2 B 2 O 7 ) have emerged as important functional materials with different properties such as catalysis, luminescence, piezo electricity, giant magneto-resistance etc. [1–3]. Among different types of pyrochlores, the ones based on lanthanide ions (Ln 3+ ) and Sn 4+ ion have got application as poten- tial host for the incorporation of luminescent lanthanide ions and such materials have got applications in flat-panel displays such as plasma display panels (PDP), field emission displays (FED), and electroluminescent (EL) devices. It will be of interest to prepare the nanoparticles of these materials and study its luminescence properties as the nanoparticles based phosphors are found to have many advantages over the bigger micron sized particles [4]. For obtaining nanoparticles of these materials it is necessary that the samples should be prepared at a relatively low temperature. There are reports on the synthesis of Ln 2 Sn 2 O 7 nanoparticles at relatively low temperatures using co-precipitation, sol gel and hydrothermal methods along with nanoparticles mediated solid state reactions [5–9]. In bulk Ln 2 Sn 2 O 7 , Ln 3+ ions are having a centrosymmetric environment (D 3d ). For lanthanide ions occupying such sites, only the magnetic dipole transitions are allowed and all electric dipole transitions are forbidden. This will result in very poor lumines- cence from Eu 3+ and Tb 3+ ions when doped in such lattices. One way to circumvent this problem is to slightly distort the lattice by aliovalent substitution. Lattice distortion results in the lowering of symmetry around the lanthanide ions and this favour an increase in the electric dipole transition probability. Since for Tb 3+ ions, all the transition are of mixed electric and magnetic di- pole in nature, it is expected that the Tb 3+ luminescence in a dis- torted Y 2 Sn 2 O 7 lattice will be better compared to undistorted Y 2 Sn 2 O 7 . In the present study Sb 3+ ions have been used to substi- tute Y 3+ ions in Y 2 Sn 2 O 7 nanoparticles doped with lanthanide ions, in order to understand the effect of iso-valent doping on the lumi- nescent properties of the nanoparticles. Sb 3+ ions have been chosen in the present study as it is having a valence shell electronic con- figuration of 5s 2 and the luminescence of ions with s 2 valence shell configurations are very sensitive to the surrounding environment [10–12]. Further it is also reported that the Sb 3+ ions can replace lanthanide ions in host like YPO 4 , LuPO 4 , LaOCl, YBO 3 etc. [13–16] and the luminescence properties of such materials strongly de- pend on the relative concentration of Sb 3+ and temperature. For example Wen et al. [16] have reported that in Sb 3+ , co-doped YBO 3 :Eu samples, nearly white light (CIE co-ordinates close to x = 0.33 and y = 0.33) can be obtained by changing the Sb 3+ to Eu 3+ ratio. In view of the above observations and inferences, it will be of interest to investigate the effect of Sb 3+ doping at Y 3+ site in the Y 2 Sn 2 O 7 :Tb nanoparticles, for its luminescence properties. Hence we have prepared very small nanoparticles of Y 2 Sn 2 O 7 doped with Tb 3+ ions and studied their luminescence characteris- tics before and after co-doping with Sb 3+ ions. 2. Experimental 2.1. Preparation of the nanoparticles For the preparation of Y 2 Sn 2 O 7 , 1.25 mol% Tb 3+ doped Y 2 Sn 2 O 7 (Y 2 Sn 2 O 7 :Tb 3+ (1.25 mol%)) and 1.25 mol% Sb 3+ co-doped Y 2 Sn 2 O 7 : 0925-3467/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2010.11.004 ⇑ Corresponding author. Tel.: +91 22 25590289; fax: +91 22 25505151. E-mail address: vsudar@barc.gov.in (V. Sudarsan). Optical Materials 33 (2011) 558–562 Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat