Synthesis and characterization of holmium doped lithium niobate powders F.Z. Fadil a,b , M. Aillerie a, * , T. Lamcharfi b , F. Abdi b a Laboratoire Mate ´riaux Optiques, Photonique et Syste `mes, Universite ´ Paul Verlaine-Metz & Supe ´lec, 2 rue E. Belin, 57070 Metz, France b Laboratoire Signaux Syste `mes et Composants, Universite ´ Sidi Mohammed Ben Abdellah, route d’Imouzzer, Faculte ´ des Sciences et Techniques de Fe `s, BP 2202, Fe `s, Morocco Received 26 November 2010; received in revised form 13 December 2010; accepted 14 March 2011 Available online 26 May 2011 Abstract Holmium doped lithium niobate (LN:Ho) powders with initial concentration of holmium in the range 0–7 mol% were synthesized by the ceramic powder processing method. Niobium penta-oxide Nb 2 O 5 , lithium carboxide LiCO 3 and holmium oxide Ho 2 O 3 with a purity of 99.99% were the starting materials. The phase content and lattice parameters of powders and ceramic pellets were characterized by X-ray diffraction (XRD). To further investigate the quality of the synthesized LN:Ho powders, the scanning electron microscopy (SEM) was used to determine the particle size and the morphology. The main results of this work point out the fact that the ceramic powder processing method is a well adapt method for obtaining high quality LN:Ho ceramics in the holmium concentration range analysed as the LiNbO 3 phase is lonely present in the ceramics at the end of the synthesized process and as their grain sizes are regular, with a maximum for the sample doped with 7 mol% of holmium. # 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Lithium niobate; Holmium doping; Ceramics 1. Introduction Lithium niobate (LiNbO 3 , LN) is an attractive material for nonlinear and integrated optics due to its interesting set of optical and physical properties. Its large electro-optic and non- linear coefficients offer a high potential for its use in various domains of modern technology such as optical wave guides, optical memories, information storage by holography and electro-optic devices [1–4]. However, when LN crystals are grown from the melt, it exists in a wide composition range and usually presents a large Li 2 O deficiency up to 4% with respect to the stoichiometric composition in the congruent crystal [5]. Therefore, a large amount of defects due to anti-sites defects – Nb in Li sites and structural vacancies necessary to obtain the charge neutrality – is present in non-stoichiometric crystals [6]. As a consequence, the LN lattice is a host for incorporation of dopants such as rare earth or metal ions, even in large concentration [7,8]. Indeed, it is known that the physical properties of LN are strongly dependent of both the intrinsic defects related to the non-stoichiometry and extrinsic defects due to impurities or dopants. Accordingly, several investiga- tions have focused on the LN physico-chemical characteriza- tion as function of the composition in pure LN and as function the nature and the concentration of single or co-doped LN in order to improve its performance in high-tech applications, including the photorefractive, non-linear optic and laser ones [9–13]. Beside all dopant elements for LN, holmium (Ho) is a promising element for applications and we can expect, combined to the advantageous intrinsic properties of LN samples, an efficient laser oscillation in the infrared region at 2.1 mm range [14–16]. At this wavelength, a transparency window of the atmosphere exists due to a lower absorption of water. For the same reasons, sensors in medicine can be considered associated, as example, in the same LN:Ho based device, a Mach–Zehnder electro-optic modulator allowing a direct numerical treatment of the measured signal and the sensor itself. In these applications where a high long/width ratio is expected to increase the efficiency of the active part of the device, lithium niobate samples growth from high quality powders or ceramics by the classical Czochralski technique or by the original micro-pulling down technique can be used [17]. For the defects controls of LN crystals and to insure a high crystalline quality of the crystals that are embedded in devices, www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 37 (2011) 2281–2285 * Corresponding author. Tel.: +33 387378565/688590694; fax: +33 387378569. E-mail address: aillerie@metz.supelec.fr (M. Aillerie). 0272-8842/$36.00 # 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2011.05.080