Birefringent and Dielectric Properties of [N(C2H5)4]2ZnBr4 and [N(C2H5)4]2CdBr4 Crystals

S. Sveleba, V. Mokryi, I. Polovinko, V. Kapustyanik Lviv State University, Lomonosov Str. 8, 290005 Lviv, Ukraine Z. Trybuła Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17/19, 60-179 Poznań, Poland P. Petrenko, G. Kiosse and V. Kravtsov Institute of Applied Physics, Acad. Sci. Moldova, Kishineu, Moldova

Received: April 15, 1992; revised version: March 16, 1993

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Dielectric and birefringent properties of [N(C2H5)4]2ZnBr4 and [N(C2H5)4]2CdBr4 crystals were investigated. It has been ascertained that two phase transitions manifest themselves in the temperature dependencies є(T) for [N(C2H5)4]2CdBr4 crystal - a second-order transition at T1 = 311 K and a first-order one - at T2 = 39 K (∆T2 = 11 K). Besides two earlier known phase transitions in [N(C2H5)4]2ZnBr4 at T1 = 350 K and Tcool2 = 282.8 K (∆T2 ≈ 2.3 K), the additional one was found at T*2 = 287.0 K, both on the cooling and heating runs. On the basis of the data about the peculiarities of dielectric and optical properties in the vicinity of T2 one can made the conclusion about the ferroelectric character of the phase, situated between T*2 and Tcool2.

DOI: 10.12693/APhysPolA.83.777 PACS numbers: 77.22.Ch, 77.22.-d, 78.20.Fm, 64.70.-p