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Subject: Activation energy × WGL Institute: IFWD ×

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Now showing 1 - 2 of 2
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    High-temperature electromechanical loss in piezoelectric langasite and catangasite crystals
    (Melville, NY : American Inst. of Physics, 2021) Suhak, Yuriy; Fritze, Holger; Sotnikov, Andrei; Schmidt, Hagen; Johnson, Ward L.
    Temperature-dependent acoustic loss Q−1 is studied in partially disordered langasite (LGS, La3Ga5SiO14) and ordered catangasite (CTGS, Ca3TaGa3Si2O14) crystals and compared with previously reported CTGS and langatate (LGT, La3Ga5.5Ta0.5O14) data. Two independent techniques, a contactless tone-burst excitation technique and contacting resonant piezoelectric spectroscopy, are used in this study. Contributions to the measured Q−1(T) are determined through fitting to physics-based functions, and the extracted fit parameters, including the activation energies of the processes, are discussed. It is shown that losses in LGS and CTGS are caused by a superposition of several mechanisms, including intrinsic phonon–phonon loss, point-defect relaxations, and conductivity-related relaxations.
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    Redox chemistry in the pigment eumelanin as a function of temperature using broadband dielectric spectroscopy
    (Cambridge : Royal Society of Chemistry, 2019) Motovilov, K.A.; Grinenko, V.; Savinov, M.; Gagkaeva, Z.V.; Kadyrov, L.S.; Pronin, A.A.; Bedran, Z.V.; Zhukova, E.S.; Mostert, A.B.; Gorshunov, B.P.
    Conductive biomolecular systems are investigated for their promise of new technologies. One biomolecular material that has garnered interest for device applications is eumelanin. Its unusual properties have led to its incorporation in a wide set of platforms including transistor devices and batteries. Much of eumelanin's conductive properties are due to a solid state redox comproportionation reaction. However, most of the work that has been done to demonstrate the role of the redox chemistry in eumelanin has been via control of eumelanin's hydration content with scant attention given to temperature dependent behavior. Here we demonstrate for the first time consistency between hydration and temperature effects for the comproportionation conductivity model utilizing dielectric spectroscopy, heat capacity measurements, frequency scaling phenomena and recognizing that activation energies in the range of ∼0.5 eV correspond to proton dissociation events. Our results demonstrate that biomolecular conductivity models should account for temperature and hydration effects coherently.