Sol–gel synthesis and characterization of sub-microsized lanthanide (Ho, Tm, Yb, Lu) aluminium garnets N. Dubnikova a , E. Garskaite b , A. Beganskiene a , A. Kareiva a,⇑ a Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania b Department of Mathematical Sciences and Technology, University of Life Sciences (UMB), P.O. Box 5003, 1432 Aas, Norway article info Article history: Received 23 December 2010 Received in revised form 4 February 2011 Accepted 7 February 2011 Available online 8 March 2011 Keywords: Holmium aluminium garnet (HoAG) Thulium aluminium garnet (TmAG) Ytterbium aluminium garnet (YbAG) Lutetium aluminium garnet (LuAG) Sol–gel preparation Aqueous processing abstract Sub-microsized and nanosized holmium aluminium garnet (Ho 3 Al 5 O 12 , HoAG), thulium aluminium gar- net (Tm 3 Al 5 O 12 , TmAG), ytterbium aluminium garnet (Yb 3 Al 5 O 12 , YbAG) and lutetium aluminium garnet (Lu 3 Al 5 O 12 , LuAG) powders were prepared by a simple aqueous sol–gel method using aluminium nitrate nonahydrate, lutetium oxide, thulium oxide, holmium oxide and ytterbium oxide as starting materials. Ethane-1,2-diol was used as complexing agent. The powder X-ray diffraction (XRD) patterns of the spec- imens sintered at 1000 °C revealed the formation of monophasic HoAG, TmAG, YbAG, and LuAG. The phase composition of the samples was also characterized by infrared (IR) spectroscopy. Microstructural features of the polycrystalline garnets were studied by scanning electron microscopy (SEM). Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Garnet structure compounds can be used as laser medium, laser radar, ceramic materials, photoelectric or medical facilities. There- fore they have attracted much attention because of their many un- ique properties and characteristics [1,2]. Well-known yttrium aluminium garnet (Y 3 Al 5 O 12 , YAG), has relatively high hardness and mechanical stability. The rare earth (RE) garnets are also poten- tial materials which have high mechanical stability like that of YAG [3,4]. Nanocrystalline YAG powders doped with Nd 3+ , Ce 3+ , Eu 3+ and Tb 3+ have found applications as promising phosphors for field emis- sion displays (FED), electroluminescent displays (ELD), vacuum fluorescent displays (VFD), plasma panel displays (PPD) and cath- ode ray tubes (CRT). The Nd 3+ -doped YAG nanopowders have found applications in fabrication of efficient laser ceramics. Also, YAG doped with different transition metal ions (Cr 4+ , Co 2+ ,V 3+ ) were studied in detail for application as new saturable absorbers in pas- sive Q-switch crystals [5–9]. The rare earth garnets are also used as laser and phosphor materials [10–16]. For example, lutetium aluminium garnet (Lu 3 Al 5 O 12 , LuAG) is widely applied as optical host material for luminescent powders or single crystals. Rare earth doped LuAG has found applications in IR lasers, phosphor converted LEDs, X-ray detectors and field emission displays. The wide application range of RE doped lanthanide garnets is due to their high mechan- ical and radiation stability, wide band gap, and excellent radiation conversion efficiency for many rare earth dopants. Eu 3+ doped LuAG due to the wide optical band gap of LuAG (6.1 eV) is of poten- tial interest as a red emitter in Xe excimer discharge lamps and plasma displays. LuAG is known to be a promising host structure for scintillating materials. This host lattice containing rare earth ions as luminescent activators, especially cerium (Ce 3+ ), yields fast decay because of the allowed 5d–4f transitions of Ce 3+ ion and is an efficient high response scintillator. However, LuAG:Ce single crys- tals are almost entirely grown from the melt (Czochralski method) by slow cooling in an expensive iridium crucible. So the growth of a high optical quality LuAG:Ce single crystal is an arduous process. It was also demonstrated, that Yb 3 Al 5 O 12 :Cr 4+ crystal is promising as a high-efficient system for tunable laser [16]. The sol–gel technology, due to its apparent advantages of fine homogeneity, high reactivity of starting materials, easier composi- tion control, lower sintering temperature and lower costs [17–20], is a promising method for the preparation of nanostructured YAG ceramics [21–24]. Recently, cerium doped lutetium aluminium garnet Lu 3 Al 5 O 12 has been synthesized using sol–gel chemistry ap- proach [25]. In the sol–gel processing of Lu 3 Al 5 O 12 ethanol, hy- drated citric acid and PEG were used as dispersant, chelating agent and crosslinking agent, respectively. The main aim of this study was to synthesize and characterize sub-microsized and nanosized lanthanide (Ho, Tm, Yb and Lu) aluminium garnets using more simple an aqueous glycolate sol–gel processing route. 0925-3467/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2011.02.008 ⇑ Corresponding author. Tel.: +370 521 93110. E-mail address: aivaras.kareiva@chf.vu.lt (A. Kareiva). Optical Materials 33 (2011) 1179–1184 Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat