Impact of Phase Transitions on Temperature Evolution of Absorption Spectra and Electron–Phonon Interactions in [N(C2H5)4]2CoCl2Br2 Crystals

被引:0
作者
V. B. Kapustianyk
S. I. Semak
S. B. Bilchenko
Yu. I. Eliyashevskyy
Yu. V. Chorniy
P. Yu. Demchenko
机构
[1] Ivan Franko National University of Lviv,Scientific
[2] Ivan Franko National University of Lviv,Technical and Educational Center of Low Temperature Studies
来源
Journal of Applied Spectroscopy | 2019年 / 86卷
关键词
absorption spectroscopy; optical absorption edge; phase transition; dielectric; cation and anion substitution; absorption coefficient; electronic transition; electron-phonon interaction;
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摘要
Absorption spectra and structural parameters of [N(C2H5)4]2CoCl2Br2 (TEACCB-2) crystals were investigated. Absorption bands corresponding to internal electronic transitions of Co2+ were identified. The impact of phase transitions on the temperature evolution of absorption spectra was studied. The low-energy tail of the absorption edge formed by ligand–metal charge-transfer electronic transitions was shown to be exponential and obeyed the empirical Urbach rule in the two high-temperature crystal phases. The temperatures and types of phase transitions at T1 = 244 K and T2 = 228 K (in cooling mode) were refined by analyzing the temperature changes of the main characteristics of the obtained spectra. An anomaly at T3 = 200 K was detected for the first time in TEACCB-2 bulk crystals and appeared earlier in the absorption spectrum of TEACCB-2 nanocrystals. It could be attributed to a phase transition.
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页码:590 / 596
页数:6
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