Journal of Physical Studies 2(1), 62–64 (1998) DOI: https://doi.org/10.30970/jps.02.62 PHYROELECTROLUMINESCENSE AND ITS INFLUENCE ON THE STRUCTURE INVESTIGATION IN THE Li2B4O7 CRYSTALS

Ya. V. Burak
Institute of Physical Optics, 23 Drahomanov Str., UA-290005, Lviv, Ukraine

A temperature dependence of a crystal lattice constant as well as a linear thermal expansion for the Li$_2$B$_4$O$_7$ (TBL) crystals were observed to have a cascade of jumps within the temperature range of 77–293 K. Some authors refer these jumps to a cascade of phases transitions in incommensurate phases. However these authors do not take into account that TBL is a very good pyroelectric material. In the given work it is proved that observable jumps are connected with piroelectric and piezoelectric byproperties of TBL. Therefore theoretical accounts of the value of the deformation of the TBL crystal for the direction [001] are conducted. It turns out that a change of the temperature of the crystal for some degrees is already sufficient for the occurence of such a value of the pyrocharge that the deformation arisen as a result of the inverse piezoelectricity could be fixed by the dilattometer. A jump will be formed at the electrical breakdown into the surrounding atmosphere at the electrical field of $10^5$ V/cm and is accompanied by pyroelectroluminescence (PEL). Thus a cascade of phase transitions in the TBL crystals in the temperature interval of 77–293 K does not exist.

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