KTiOPO₄-FAMILY CRYSTALS

KTiOPO₄ single crystal
 

KTiOPO₄ (KTP) and other crystals of this family are of great interest as new effective materials for nonlinear optics and are intensively studied in the last time. Their high nonlinear optical susceptibility suggests existence of ferroelectric properties and, indeed, the second order ferroelectric phase transitions were observed for the first time in our laboratory for KTiOPO₄, RbTiOPO₄ and TlTiOPO₄ crystals. The most effective methods to study these transitions are measurements of dielectric permeability and thermooptical studies. Similar transitions were thereafter observed in many other crystals of this family. They can lead to formation of ferroelectric domains and to accidental variations of physical properties. At the same time ferroelectric properties of the KTP - family crystals can be used in practical purposes such as production of optical elements with a specified domain configuration.

One of peculiarities of KTP-family crystals, especially of flux grown ones, is also their anomalous high ionic conductivity due to presence of movable K⁺ or other alkaline cations which can be regulated in wide limits by means of heterovalent substitutions. Hence these crystals may be regarded as representatives of a new type of solid state materials: ferroelectrics - superionic conductors. Recently we observed also in the KTiOPO₄ crystals doped with 3-5 at.% of niobium jumps of electrical conductivity up to 2-3 orders of magnitude which is typical for some other superionics.

The main attention in 2004 was paid to growth and study of physical properties of doped crystals of the KTP family. The single crystals of KTP with Na, Rb, Tl, Ge, Sn, Nb, Ta, Sb, Zr, Hf and RTP with Cs, Nb, Zr were grown. Ferroelectric, conductive and non-linear properties of doped KTP family crystals are structure sensitive properties. For example, X-ray analysis of Nb and Sb-doped KTP crystals revealed the presence of extra potassium positions. This leads to the increase of electrical conductivity and relaxation phenomena. KTP crystals doped by Zr, Hf show a lager second harmonic generation  than pure KTP.

Anomalies of dielectric permeability at the ferroelectric phase transitions in the crystals KTiOPO₄ (1), RbTiOPO₄ (2) and TlTiOPO₄ (3).

Main publications:

1. Yanovskii V.K. and Voronkova V.I. Ferroelectric phase transitions and properties of crystals of the KTiOPO₄ family // Phys. stat. sol. (a). 1986. V. 93. P. 665.

2. Voronkova V.I. and Yanovskii V.K. Morphology of KTiOPO₄ crystals // Kristallographiya. 1986. V. 31. P. 207.

3. Voronkova V.I., Gvozdover R.S., and Yanovskii V.K. Ferroelectric domains in the KTiOPO₄ and RbTiOPO₄ crystals // Pis'ma JTF. 1987. V. 13. P. 934.

4. Voronkova V.I. and Yanovskii V.K. Flux growth and properties of the KTiOPO4 family crystals. // Neorg. mater. 1988. V. 24. P. 273.

5. Pisarev R.V., Markovin P.A., Shermatov B.N., Voronkova V.I., and Yanovskii V.K. Thermooptical study of KTiOPO₄ family crystals // Ferroelectrics. 1989. V. 96. P. 181.

6. Voronkova V.I., Schubentsova E.S., and Yanovskii V.K. Ferroelectric and physicochemical properties of the K_1-xNa_xTiOPO₄, K_1-xTl_xTiOPO₄, and Rb_1-xCs_xTiOPO₄ solid solutions. // Neorg. mater. 1990. V. 26. P. 143.

7. Sil'verstova I.M., Pisarevskii Yu.V., Voronkova V.I., Yanovskii V.K. Piezoelectric, elastic and dielectric properties of RbTiOPO₄ crystals // Kristallographiya. 1990. V. 35. P. 229.

8. Voronkova V.I., Yanovskii V.K., Sorokina N.I., Verin I.A., and Simonov V.I. Ferroelectric phase transition and atomic structure of KGeOPO₄ crystals // Kristallographiya. 1993. V. 38. P. 147.

9. Liu Wen, Voronkova V.I., Yanovskii V.K., Sorokina N.I., Verin I.A., Simonov V.I. Synthesis, atomic structure, and properties of crystals in the RbTiOPO₄ - CsTiPO₅ system // Crystallography Reports. 2000. V. 45. No. 3. P. 380 - 385.

10. Voronkova V.I., Yanovskii V.K., Losevskaya T.Yu., Stefanovich S.Yu. Electrical and nonlinear optical properties of KTiOPO₄ single crystals doped with Nb or Sb. // J. Appl. Phys. 2003. V. 94. No. 3. P. 1954-1958.

11. Voronkova V.I., Yanovskii V.K., Losevskaya T.Yu, Stefanovich S.Yu., Zverkov S.A., Alekseeva O.A., Sorokina N.I. Electrical and nonlinear optical properties of KTiOPO₄ single crystals doped with niobium, antimony and tantalum // Crystallography Repots. 2004. V. 49. No. 1. P. 123-129.

12. Voronkova V.I., Yanovskii V.K., Leontieva I.N. Agapova E.I., Kharitonova E.P., Stefanovich S.Yu., Zverkov S.A. Growth and properties of KTiOPO₄ single crystals doped with zirconium // Inorganic Materials. 2004. V. 40. No 12. P. 1505 - 1507.

13. Sorokina N.I., Voronkova V.I. Structure and properties of crystals in the potassium titanyl phosphate family: a review. // Crystallography Reports. 2007. V. 52. No. 1. p. 80-93.