UNSPECIFIED (1996) A new Kosters prism interferometer for simultaneous determination of refractive index and thermal expansion of crystals as a function of temperature. JOURNAL OF APPLIED CRYSTALLOGRAPHY, 29 (Part 5). pp. 574-583. ISSN 0021-8898

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Abstract

An uniquely-modified Kosters prism interferometer for the simultaneous and independent measurement of refractive index, delta n(T), and thermal expansion, delta l(T), as a function of temperature in the range 308-1273 K, is described. The capabilities of the system are demonstrated via measurement of delta n(T) and delta l(T) along both the [100] and [001] directions up to and through the alpha-beta phase transition in quartz, with results in good agreement with previous measurements. Further to this, experiments to determine delta n(T) and delta l(T) along the [100], [010] and [001] directions in the orthorhombic nonlinear optical crystal indium-doped KTiOAsO4 are described. The results are used to show that the ferroelectric-paralectric phase transition at T-c = 1063 K is second-order and exhibits Landau-type behaviour over a range of 100 K below T-c. Finally, similar experiments on the orthorhombic crystal Ba2NaNb5O15 are reported. The behaviours of delta n(T) and delta l(T) at the ferroelastic phase transition at 563 K and the ferroelectric-paraelectric phase transition at T-c = 849 K are discussed. Clear evidence of the existence of polar fluctuations in the paraelectric phase is presented.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Journal or Publication Title:	JOURNAL OF APPLIED CRYSTALLOGRAPHY
Publisher:	MUNKSGAARD INT PUBL LTD
ISSN:	0021-8898
Date:	1 October 1996
Volume:	29
Number:	Part 5
Number of Pages:	10
Page Range:	pp. 574-583
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/18296

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