I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Kola Science Centre of RAS (ICHTREMS KSC RAS)

S. M. Masloboeva, Senior Researcher, e-mail: sofia_masloboeva@mail.ru

V. T. Kalinnikov, Director

O. A. Zalkind, Researcher

G. I. Kadyrova, Researcher

V. Ya. Kuznetsov, Researcher

Lithium niobate crystals are widely applied in integral optics, acoustic electronics and other fields. The crucial factor to be considered here is enhancing the LiNbO₃ optic homogeneity and laser damage resistance. This work has focused on developing the synthesis methods for high-purity niobium (V) oxide containing trace amounts of Zn²⁺ ions with intended concentrations, and on studying the phase composition of products synthesized. To obtain a Nb₂O₅:Zn alloy, two methods of introducing the photovoltage-inactive Zn²⁺ cations have been investigated. By the first method, zinc oxide was added to a highly pure niobium-containing solution (re-extract) during the solvent extraction of lithium niobate, or rare-metal, processing wastes. The method can be applied in concentrating Zn²⁺ in Nb₂O₅ ~1.7 w/o. The other method involves mixing a high-purity niobium hydroxide with a nitric-acid zinc solution, with a zinc concentration sufficient to produce Nb₂O₅:Zn²⁺ of a target composition at a certain Т:Vs ratio. A flow sheet has been developed for alloying highly pure niobium hydroxide with Zn2+ ions, applicable within the entire range of studied concentrations (Nb₂O₅:0.3÷4.87 w/o ZnО). Optimal conditions for individual process stages have been determined. The phase composition of the Nb₂O₅:Zn alloys synthesized have been analyzed using IR spectroscopy and X-ray phase analysis. At Zn²⁺ contents in Nb₂O₅ of 1.9% upwards, another phase (in addition to the basic Nb₂O₅), having the ZnNb₂O₆ composition, was noted to emerge, its share increasing with growing Zn²⁺ concentration. There have been prepared experimental samples of niobium pentoxide for synthesizing a lithium niobate charge and growing LiNbO₃ crystals with improved optic characteristics and a low photorefraction effect.

1. Schirmer O. F., Thiemann O., Wöhlecke М. Journal of Physical Chemistry of Solids. 1991. Vol. 52. pp. 185–200.

2. Volk T., Wöhlecke М., Rubinina N. et al. Ferroelectrics. 1996. Vol. 183. pp. 291–300.

3. Sidorov N. V., Volk T. R., Mavrin B. N. et al. Niobat litiya : defekty, fotorefraktsiya, kolebatelnyy spektr, polyaritony (Lithium niobate : defects, photorefraction, vibration spectrum, polariton). Moscow : Nauka, 2003. 255 p.

4. Palatnikov M. N., Sidorov N. V., Kalinnikov V. T. Tsvetnye Metally – Non-ferrous metals. 2000. No. 10. pp. 54–60.

5. Kuzminov Yu. S., Osiko V. V. Kristallografiya – Crystallography Reports. 1994. Vol. 39, No. 3. pp. 530–535.

6. Masloboeva S. M., Arutyunyan L. G. Vestnik Murmanskogo Gosudarstvennogo Tekhnicheskogo Universiteta – Bulletin of Murmansk State Technical University. 2010. Vol. 13, No. 4/2. pp. 907–912.

7. Kato K. Acta Crystallography Section B. 1976. Vol. 32. pp. 764–767.

8. Pollard A. J. Journal of American Ceramics Society. 1961. Vol. 44, No. 12. p. 630.

9. Norin R., Dahlen B. Acta Chemica Scandinavica. 1969. Vol. 23, No. 5. pp. 1826–1827.