Cryst. Res. Technol. 44, No. 5, 463 – 468 (2009) / DOI 10.1002/crat.200800604 © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Flux growth and characterization of Ti- and Ni-doped forsterite single crystals A. Bloise*, E. Barrese, C. Apollaro, and D. Miriello Dipartimento di Scienze della Terra, Università della Calabria - Via Pietro Bucci, 87036 Arcavacata di Rende (CS), Italy Received 13 December 2008, revised 23 January 2009, accepted 5 February 2009 Published online 20 February 2009 Key words flux crystal growth, Ti-doped forsterite crystals, Ni-doped forsterite crystals. PACS 81.10.-h, 61.72.Ww Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO 3 , V 2 O 5 , Li 2 CO 3 ) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single-crystal X-ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h -1 . These synthetic, well-characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Forsterite (Mg 2 SiO 4 ) is the magnesium-rich end-member of the olivine solid-solution family and the major component of the earth’s upper mantle [1]. The crystalline structure of forsterite is based on a nearly hexagonal close-packed array of oxygens with Si in the tetrahedral and Mg in the octahedral sites, and crystallizes in the orthorhombic system with space group Pnmb. There are two kinds of Mg-octahedral sites, M1 (Ci symmetry) and M2 (Cs symmetry), M1 being smaller than M2 [2]. Forsterite crystals, owing to their good properties, e. g. refractoriness (melting point 1890 °C), low dielectric permittivity, low thermal expansion, and chemical stability, are ideal substrates in electronics and optimal materials for thermal insulation in applications at high temperatures. The usual presence of foreign ions (Fe, Ni, Mn, etc.) in natural forsterite and their inconstant amounts, may inhibit as high-performance materials. For these reasons, pure and doped forsterite have been grown by several researchers [3-8] with differing methods (e.g., Czochralski methods, sol-gel, co-precipitation, etc.). The synthesis and characterization of forsterite doped with transition metal ions has also been an important subject in recent years [9-11], since potential use have been found in laser optics [12]. It has been calculated that, in Ti-doped forsterite crystals grown by Czochralski methods, the concentration of Ti 3+ ions on site M2 is ten times greater than that on site M1[13]. Such crystals may have useful applications for lasers in the future. Ni-doped forsterite, which may also be used in tunable lasers, grown by the floating zone technique, shows that Ni 2+ ion preferentially substitutes for Mg in the centrosymmetric M1 site at low concentrations [14] although, at higher concentrations, M2 site is also occupied [15]. So far, doped forsterite has been synthesized in various experimental conditions, mainly to study its spectral and luminescent properties and not to define in detail the kinetic process allowing their growth. The purpose of the present work was to optimize the ____________________ * Corresponding author: e-mail: andrea.bloise@unical.it