Spectral diagnostics of vibrational centers in crystals with hydrogen bonds

Abstract

In practical application of crystals in optoelectronics and laser technology it is necessary to know the direction of optical axes and types of oscillatory centers, which is a relevant and necessary condition. In this paper, the infrared spectra of transmission and absorption of hexagonal crystals of lithium iodate α-LiIO3, grown by open evaporation in H2O and D2O solutions, as well as natural lamellar crystals of phlogopite and muscovite monoclinic crystal are investigated. The band gap width of the investigated crystals is determined by transmission spectra. In the absorption spectra there were determined activation energy and wavelength of the oscillatory centers that are associated with the vibrations of protons, hydronium ions Н3О+, protium H+, OH groups and molecules HDO. The good correlation of the parameters of infrared spectra with the spectra of thermally stimulated depolarization currents and NMR spectra has shown. The possibility of diagnostics of types of oscillatory centers by means of infrared spectra is considered, which also allows to find out the direction of optical axes. The obtained results allow to use IR spectra to determine not only the types of vibrational centers, but also the presence of anisotropy of the crystal lattice of the studied crystals.

Technology of thermally stimulated diagnostics of anisotropy and optical axes in crystals

“…Thus pyroelectric current (maxima 1 and 2) dominates over weak relaxation current by 3-4 orders of magnitude. The activation energies (Table 1) calculated from the TSD spectra agree well with the activation energies calculated from infrared spectra [13,14].…”

“…The use of the thermally stimulated depolarization current method allowed completely solving the tasks of this work and puts forward a technology for the diagnostics of anisotropy and optical axes in crystalline materials. The technology developed in this work is doubtlessly of interest for the fundamental research dealing with the tunneling effect and for various practical applications as a method of examining the quality of optical crystals at a sufficiently high scientific and technical level that was unachievable before, resulting in the consequent development of the method of optical diagnostics of optical axes and types of oscillation centers in crystals with hydrogen bonds [13,14].…”

Technology for thermostimulated diagnostics of anisotropy and optical axes of crystals

“…Следовательно, в данном случае пироэлектрический ток (максимумы №№ 1 и 2) перекрывает слабый релаксационный ток, превышая его на 3-4 порядка. В результате были получены значения энергии активации (таблица), хорошо коррелирующие со значениями, полученными по инфракрасным спектрам [13,14].…”