Crystal Research and Technology
Cryst. Res. Technol. 41, 344 (2006) - Abstract -

Study on the ferroelectric phase transition in potassium lithium niobate (KLN)

S. Podlojenov, J. Stade, M. Burianek, and M. Mühlberg

University of Cologne, Institute of Crystallography – Zülpicher Str. 49b, 50674 Cologne, Germany

Keywords tetragonal tungsten bronzes, non-linear optic materials, ferroelectric phase transition, potassium lithium niobate
PACS 42.70.Mp, 77.84.Dy, 81.10.Fq
DOI 10.1002/crat.200510585

The ferroelectric phase of potassium lithium niobate K3Li2-xNb5+xO15+2x (KLN) in the range of 0.15 < x < 0.5 is a very promising material for the second harmonic generation (SHG) in the blue visible region (~ 410 nm). The ferroelectric phase transition was shown to occur between 400 and 500°C depending on the composition of the KLN phase. In this study several analysis techniques were used to investigate the phase transition on ferroelectric (x=0.3) KLN samples. The temperature-dependent measurements of the relative dielectric constant provided a phase transition temperature of about 470°C. In our DTA experiments, a small but reproducible thermal effect at the phase transition in KLN was indicated. The temperature-dependent birefringence measurement technique, applied the first time on KLN, shows a second order behaviour at a temperature of 467°C. However, this phase transition is accompanied by a small thermal effect. The DSC analysis for the other KLN composition (x=0.5) provided a phase transition temperature of 514°C. The appearance of a phase transition in the paraelectric KLN phase (Nb content higher than 55 mol %) was also studied.




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