Materials Science and Engineering A 403 (2005) 182–185 Luminescence study of iron doped lithium aluminate phosphor N. Suriyamurthy a , B.S. Panigrahi b,∗ , A. Natarajan a a Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, India b Reactor Operation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, India Received in revised form 26 April 2005; accepted 12 May 2005 Abstract -Lithium aluminate phosphors doped with iron were prepared through solid-state and combustion routes. In case of combustion process, urea and citric acid were used as fuels. Preparation of lithium aluminate through combustion was not dependent on mass to volume ratio. Luminescence intensity was maximum for samples prepared through solid-state reaction route. © 2005 Elsevier B.V. All rights reserved. Keywords: Combustion synthesis; LiAlO 2 :Fe; Iron luminescence 1. Introduction The compound LiAlO 2 is known to exist in three possible allotropes, namely -LiAlO 2 , the low temperature (400 ◦ C) form; -LiAlO 2 , the intermediate temperature (400–800 ◦ C) form; -LiAlO 2 which is the most stable form at high tem- perature (>1000 ◦ C). -LiAlO 2 is a potential candidate for breeding tritium in a nuclear fusion reactor due to its chem- ical and thermal stability as well as less radiation damage property [1,2]. This apart, -LiAlO 2 doped with iron emits in the deep red region rendering it suitable for artificial plant illumination phosphor blends as light peaking around 730 nm is essential for optimum plant growth and flowering [3]. Con- ventionally, this is prepared by solid-state reaction method. The solid-state reaction method is generally based on mixing of fine powder ingredients and followed by high temperature heating of the mixture. Later, some wet chemical and com- bustion synthesis methods were reported to be better than the solid-state reaction methods due to intimate mixing of reactants, high product purity and low processing tempera- ture [4–7]. In the present study, we have prepared -LiAlO 2 doped with Fe 3+ through both the solid-state reaction route and combustion route. The combustion synthesis was carried out using urea and citric acid as fuel. The optical spectroscopy ∗ Corresponding author. Tel.: +91 4114 280358; fax: +91 4114 280336. E-mail address: bsp@igcar.ernet.in (B.S. Panigrahi). of the iron incorporated as an impurity in host materials has received much attention in the literature [8,9]. The lumines- cence of iron doped in -LiAlO 2 is studied in this paper. 2. Experimental procedure 2.1. Solid-state synthesis The stoichiometric amount of lithium nitrate and alu- minum nitrate were finely ground and to it required amount of ferric perchlorate was added. The mixture was pre-fired at 800 ◦ C for 10 h in open atmosphere and then again ground. The preheated sample was again heated at 1260 ◦ C in open atmosphere for 10 h. The resultant powder product was white in color. 2.2. Combustion synthesis Required quantities of lithium nitrate and aluminum nitrate solutions were taken in a 100 ml capacity platinum crucible and stirred well to get a homogeneous solution. About 2 g of urea was then added to this solution. Fol- lowing the dissolution of urea, the content was transferred into a 250 ml platinum container. This container was heated under an infrared lamp until the liquid was evaporated. The remaining pasty mixture was placed in a muffle furnace main- 0921-5093/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2005.05.016