Structure of KTiOPO 4 single crystals grown by the top-seeded solution and spontaneous flux crystallization methods
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CTURE OF INORGANIC COMPOUNDS
Structure of KTiOPO4 Single Crystals Grown by the Top-Seeded Solution and Spontaneous Flux Crystallization Methods N. E. Novikovaa, I. A. Verina, N. I. Sorokinaa, O. A. Alekseevaa, V. I. Voronkovab, M. Tseitlinc, and M. Rothd a Shubnikov
Institute of Crystallography, Russian Academy of Sciences, Leninskiœ pr. 59, Moscow, 119333 Russia e-mail: [email protected] b Moscow State University, Moscow, 119992 Russia c Ariel University Center of Samaria, Ariel, Israel d Faculty of Science, The Hebrew University of Jerusalem, Jerusalem, Israel Received October 25, 2007
Abstract—This paper reports on the results of precision X-ray structural investigations of KTiOPO4 single crystals grown by one method (crystallization from a solution in the melt) in two variants (the spontaneous formation of crystallization centers or top-seeded solution growth during slow cooling of saturated solution melts). It is shown that spontaneous flux crystallization leads to the formation of a larger number of defects. Potassium atoms are found to be disordered. The splitting of the K1 and K2 potassium positions is equal to 0.347(4) and 0.279(3) Å, respectively, for the crystals grown by the top-seeded solution method and 0.308(5) and 0.321(4) Å, respectively, for the crystals grown through the spontaneous flux crystallization. PACS numbers: 61.66.Fn, 42.70.Mp, 66.30.Dn, 77.80.Bh DOI: 10.1134/S1063774508060060
INTRODUCTION In the last thirty years, crystals belonging to the family of potassium titanyl phosphate KTiOPO4 (KTP) have attracted the particular attention of researchers throughout the world owing to their unique physical properties, such as the ferroelectric, superionic, and nonlinear optical properties [1–3]. These crystals have been widely used in continuous-wave and pulsed Nd3+ lasers for doubling the radiation frequency and in optical waveguides employed in integrated optics. Moreover, these crystals are excellent high-quality materials for use in scientific investigations, because they have a mechanical strength, a high chemical and thermal stability, and resistance to high-intensity laser radiation. In the last few years, there have appeared a considerable number of papers devoted to the synthesis of KTP crystals doped with isovalent or heterovalent impurities, as well as to the investigation of their properties and structure with the aim of improving the nonlinear optical characteristics of crystals and understanding the factors responsible for the manifestation of these properties [4–7]. To date, it has been established that the unique properties of crystals belonging to the family of potassium titanyl phosphate are associated with the specific features of their crystal structure. The structure of KTP crystals represents a three-dimensional rigid framework formed by chains of alternating vertex-shared titanium–oxygen octahedra TiO6 and phosphorus–oxy-
gen tetrahedra PO4. The framework of the crystal structure contains wide helical channels that are extended along the c axis of the crystal and occ
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