Complex study of the structural and optical homogeneity of lithium niobate crystals
- PDF / 992,096 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 104 Downloads / 202 Views
AL PROPERTIES OF CRYSTALS
Complex Study of the Structural and Optical Homogeneity of Lithium Niobate Crystals N. V. Sidorova, M. N. Palatnikova, A. A. Yanicheva, A. A. Gabaina, O. V. Makarovaa, and O. Yu. Pikul’b a
Tananaev Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Science Center, Russian Academy of Sciences, Apatity, Murmansk oblast, 184209 Russia email: [email protected] b Far Eastern State Transport University, Khabarovsk, Russia Received April 24, 2013
Abstract—Methods of Raman spectroscopy, laser conoscopy, optical microscopy, and electron spin reso nance have been used to study the photorefractive properties and structural and optical homogeneity of the following lithium niobate (LiNbO3) crystals: nominally pure crystals of congruent composition (LiNbO3con); LiNbO3:Cu[0.015 wt %] crystals grown from a melt of congruent composition and nominally pure crystals of stoichiometric composition grown from a melt with 58.6 mol % Li2O (LiNbO3st). A small deformation of optical indicatrix and regular microdomain structures of fractal type are revealed for the LiNbO3:Cu[0.015 wt %]; the microdomain structures may be due to the nonuniform impurity incorporation into the structure. It is shown that oxygen octahedra in the LiNbO3:Cu[0.015 wt %] crystal are deformed in comparison with the octahedra in LiNbO3st and LiNbO3con crystals and that the main and impurity cations are clusterized along the polar axis. It is established that the LiNbO3:Cu[0.015 wt %] crystal exhibits photo refractive properties not only due to the presence of intrinsic defects with localized electrons, as in the case of LiNbO3st, but also due to the charge exchange in copper cations (Cu2+ Cu+) under illumination. DOI: 10.1134/S1063774514050162
INTRODUCTION Lithium niobate (LiNbO3) is a crystalline phase of variable composition; it is characterized by a wide homogeneity range in the phase diagram, which makes it possible to grow crystals with different Li/Nb ratios [1, 2]. LiNbO3 crystals (independent of compo sition) have a defectrich structure: they always con tain point and cluster defects; micro and macrostruc tures of different origins; and charged defects with localized electrons, the character of which is deter mined by the crystal composition and growth condi tions [2–5]. In addition, these crystals are generally characterized by the nonuniform volume distribution of intrinsic and impurity defects [2, 6, 7]. Promising photorefractive materials are ferroelectric lithium nio bate crystals of stoichiometric composition (LiNbO3st, R = Li/Nb = 1), as well as crystals of congruent com position (LiNbO3con, R = Li/Nb = 0.946) doped with copper (LiNbO3:Cu) [2, 4–10]. Copper cations are multiply charged and may undergo charge exchange Cu+) [9]. However, the under illumination (Cu2+ photorefractive properties of LiNbO3:Cu single crys tals practically have not been studied. Specifically, photorefractive (photoinduced) light scattering (PRLS) was generally investigated [8, 9]. The
Data Loading...
