Yttria stabilized Al 2 O 3 –ZrO 2 eutectic crystal fibers grown by the laser heated pedestal growth (LHPG) method A. Laidoune a, * , K. Lebbou b , D. Bahloul a , M. Smadi a , M. Zereg a a Laboratoire de Physique des Rayonnements et leur Interaction avec la Matière PRIMALAB, Université de Batna, 05000 Batna, Algérie b Laboratoire de Physico-Chimie des Matériaux Luminescents LPCML, Université de Lyon, Université Lyon1, UMR CNRS 5620, Bât.Kastler, 69622 Villeurbanne, France article info Article history: Received 20 May 2009 Accepted 15 October 2009 Available online 3 March 2010 Keywords: Fiber LHPG Alumina Zirconia Eutectic abstract In this work, yttria doped Al 2 O 3 /ZrO 2 eutectic crystal fibers were grown using the laser heated pedestal growth (LHPG) method. Two yttria concentrations (3 mol% and 9 mol% Y 2 O 3 ) have been examined. Eutec- tic fibers 0.4–1 mm in diameter and up to 40 mm in length have been grown with pulling rate of 0.1– 30 mm/min. The aim of this work was to obtain well-controlled microstructure from liquid phase. LHPG method allows us using of relatively high pulling rates compared with other growth methods. The opti- mal laser power corresponding to each concentration has been determined versus the pulling rate. Using X-ray powders diffraction at room temperature, the phases were identified as tetragonal one for zirconia and a-alumina for Al 2 O 3 . The fibers microstructure has been characterized by scanning electron micro- scope (SEM). The micro-structural pattern was irregular Chinese-script for both concentrations with a cellular arrangement for the higher concentration. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction In several applications, composite materials systems are very useful because of their good properties: high strength combined with high toughness at high temperatures [1,2]. Depending on the position in the equilibrium diagram, oriented solidified eutec- tic materials contain different phases distributed as lamellae or fi- bers with a host phase. Quite often, the single crystal phases grow along well-fixed direction to minimize the interfacial energy and especially to generate the wanted application. The eutectic micro- structure consists of either single crystal rods or lamellae embed- ded in a single host. In this regard, several compounds were studied and many results were reported for Al 2 O 3 -based eutectic systems. The Al 2 O 3 –ZrO 2 composites are good candidates for high temperature applications where a combination of strength, ther- mal stability and chemical inertness are required [3–5]. The Al 2 O 3 –ZrO 2 eutectics are also interesting because they can accept high amount of yttrium [2]. Yttria stabilized Al 2 O 3 –ZrO 2 eutectic fibers have considerably better mechanical properties than Al 2 O 3 –ZrO 2 and Al 2 O 3 –YAG fibers [6]. Significant improvements of both toughness and strength were also obtained when tetrago- nal ZrO 2 is added. Several methods have been used for the growth of eutectic materials (Bridgman [7–9], floating molten zone [2,10] and micro-pulling-down techniques [5,6]). The eutectic structures are complex and different morphology can be observed such as lamellar, Chinese-script and rod-like structures [5,11–13]. Type of the structure depends on the growing conditions (pulling rate, temperature of the melt and yttria concentration). The strength- controlling micro-structural parameters depend on the growth conditions that determine the eutectic morphologies. In this work we have grown the Y 2 O 3 doped Al 2 O 3 –ZrO 2 eutectic fiber using the laser heated pedestal growth (LHPG) method [14] with various amounts of yttria and different crystallization rates. Our target was to obtain thin crystalline fibers that have certain fi- brous microstructure suitable for optical applications based on the eutectic structure. In spite of the fact that the development of opti- cal materials using eutectic structure is complex, the existence of well-defined eutectic microstructure for a wide range of materials make such substance a promising candidate for the development of new devices. 2. Experimental The experimental apparatus is shown in Fig. 1. The eutectic crystal fibers were grown at air atmosphere using the laser heated pedestal growth (LHPG) method. In this technique, the raw mate- rial rods are heated using a high power CW-CO 2 laser beam. The 10.6 lm laser beam is focused by means of circularly symmetric optics to produce a very homogeneous distribution of the radiation on the rod [15]. The laser beam has enough power (up to 200 W) to melt the top of the rod creating a small molten zone (about 1 Â 1 Â 1 mm 3 ) where a seed crystal is immersed. Once the inter- facial tension forces between the molten zone and the seed are in 0925-3467/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2010.02.003 * Corresponding author. E-mail address: laidoune@univ-batna.dz (A. Laidoune). Optical Materials 32 (2010) 731–734 Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat