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High-temperature phase transitions, switchable dielectric behaviors and barocaloric effects in three new organic molecule-based crystals

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Abstract

Three new organic molecule-based compounds, ethyl-trimethyl-phosphonium picrate (1, [ETtmp][picrate]), hydroxymethyl-trimethyl-phosphonium picrate (2, [HMtmp][picrate]), and cyclopentyl-trimethyl-phosphonium picrate (3, [CPtmp][picrate]), have been corroborated as high-temperature phase transition materials possessing switchable dielectric behaviors. Compounds 1, 2 and 3 undergo dielectric anomalies which could be tuned in two pronounced dielectric states and switched by reversible phase transitions at 320.8 K, 393.9 K and 398.1 K, respectively. For compounds 1, 2 and 3, not only the phase transition temperatures but also the magnitudes of the dielectric anomalies presented variations by regulating the guest cations. The respective dielectric constants in the high dielectric states are 1.6, 2.7 and 3.6 times those in the low dielectric states for compounds 1, 2 and 3. And considering the big entropy changes (ΔS) in the three title compounds, we predicted the sensitivities of the phase transition temperatures (Tc) to the applied pressure. And the estimated barocaloric coefficients (δTcP) in the three title compounds indicate that they potentially perform barocaloric effects of interest for cooling applications under adequate pressure.

Graphical abstract: High-temperature phase transitions, switchable dielectric behaviors and barocaloric effects in three new organic molecule-based crystals

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Publication details

The article was received on 01 Aug 2018, accepted on 10 Nov 2018 and first published on 12 Nov 2018


Article type: Paper
DOI: 10.1039/C8NJ03845G
Citation: New J. Chem., 2019, Advance Article
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    High-temperature phase transitions, switchable dielectric behaviors and barocaloric effects in three new organic molecule-based crystals

    R. Li, L. Zhou, P. Shi, X. Zheng, J. Gao, Q. Ye and D. Fu, New J. Chem., 2019, Advance Article , DOI: 10.1039/C8NJ03845G

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