Acta Crystallographica Section B

Structural Science

Volume 59, Part 3 (June 2003)

research papers

Acta Cryst. (2003). B59, 353-360 [ doi:10.1107/S0108768103008450 ]

Cation movement and phase transitions in KTP isostructures; X-ray study of sodium-doped KTP at 10.5 K

S. T. Norberg, A. N. Sobolev and V. A. Streltsov

Abstract: An accurate structure model of sodium-doped potassium titanyl phosphate, (Na_0.114K_0.886)K(TiO)₂(PO₄)₂, has been determined at 10.5 K by single-crystal X-ray diffraction. In addition to the low-temperature data, X-ray intensities have been collected at room temperature. When the temperature was decreased from room temperature to 10.5 K, both potassium cations moved 0.033 (2) Å along the c-axis, i.e. in the polar direction within the rigid Ti-O-P network. This alkaline metal ion displacement can be related to the Abrahams-Jamieson-Kurtz T_C criteria for oxygen framework ferroelectrics. Potassium titanyl phosphate (KTP) is a well known material for second harmonic generation (SHG), and the influence of sodium dopant on the TiO₆ octahedral geometry and SHG is discussed. The material studied crystallizes in the space group Pna2₁ with Z = 4, a = 12.7919 (5), b = 6.3798 (4), c = 10.5880 (7) Å, V = 864.08 (9) Å³, T = 10.5 (3) K and R = 0.023.

Keywords: alkaline titanium phosphate structure; cation movement; phase transitions; temperature change; second harmonic generation.


	Structure factor file (CIF format) (72.6 kbytes) Contains datablock RT

	Structure factor file (CIF format) (420.5 kbytes) Contains datablock 10K

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