Ionic Plasma Model of Low-Energy Excitationin Cation Superionic Conductors

Kobayashi, Michisuke; Tomoyose, Tomozo; Aniya, Masaru

doi:10.1143/jpsj.60.3742

Cited by 12 publications

(6 citation statements)

References 22 publications

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“…2) The magnitude of WL is in the range of 2 to 6meV and is proportional to M-'/2, 3) For SIC with the same species of mobile ion, WL is not sensitive to the crystal strucBased on the above observations, Kobayashi et al [3] have proposed the ionic plasma model for the LEE in cation SIC. In this model, the LEE is interpreted as being a plasma oscillation of cations on the anion background.…”

Section: Pressure and Temperature Dependences Of The Low Energy Excitmentioning

confidence: 99%

Pressure and temperature dependences of the low energy excitation in superionic conductors based on the ionic plasma model

Aniya

Tomoyose

Kobayashi

1996

Physica Status Solidi (b)

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Superionic conductors form a particular class of solid materials characterized by ionic conductivities of an order of magnitude as is usually found in molten salts. There, the high ionic conductivity is due to the movement of one kind of ions between sites provided by the immobile ion sublattice. A low energy excitation (LEE) mode has been observed in many cation superionic conductors (SIC) by making use of inelastic neutron scattering experiments [l, 21. Many models of LEE have been proposed till now [2]. However, concerning the origin of LEE, there is no general consensus. 1) W L is almost independent of wavenumber.2) The magnitude of WL is in the range of 2 to 6meV and is proportional to M-'/2, 3) For SIC with the same species of mobile ion, WL is not sensitive to the crystal strucBased on the above observations, Kobayashi et al.[3] have proposed the ionic plasma model for the LEE in cation SIC. In this model, the LEE is interpreted as being a plasma oscillation of cations on the anion background. It must be remarked here that by the term "anion background", we are not considering a uniform background as in the case of the well-known electronic plasma oscillations. The LEE is viewed as a collective motion of cations in a cage formed by anions. In the present note, the pressure and temperature dependences of the LEE in SIC are studied based on the ionic plasma model. E~M ]Kumamoto 860, Japan. Okinawa 903-01, Japan. Niigata 950-21, Japan.

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Section: Pressure and Temperature Dependences Of The Low Energy Excitmentioning

confidence: 99%

Pressure and temperature dependences of the low energy excitation in superionic conductors based on the ionic plasma model

Aniya

Tomoyose

Kobayashi

1996

Physica Status Solidi (b)

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“…In Cu chalcogenides the low-energy modes were originally observed in inelastic scattering experiments by Sakuma et al 2) in Cu 2 Se and assigned to localized vibrations. The ion plasma excitations 3) or transverse optic modes, as in anion conductors 4) , may also be responsible for the low-energy peak in density of states. To clarify the situation measurements of the phonon density of states have been performed in Cu 1.78 Se and Cu 2 Se powder samples using a multidetector time-of flight spectrometer.…”

Section: Introductionmentioning

confidence: 99%

Phonon Dispersion in Superionic Copper Selenide: Observation of Soft Phonon Modes in Superionic Phase Transition

2010

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This paper reports lattice dynamical measurements of Cu 1.8 Se superionic conductor in the superionic -phase at ambient temperature. Measurements of phonon dispersion curves were performed with the new triple-axis spectrometer, TAIPAN, at the OPAL reactor. We found that TA [100], TA [111] and TA 1 [110] phonon branches demonstrate a decrease in frequency at wavevectors q > 0.5 rather than the flattening observed previously. Results are compared with calculated density functional theoretical calculations showing the presence of unstable soft mode related to ordering of Cu atoms observed in Cu 1.8 Se at room temperature followed byphase transition at a lower temperature. Superstructure arising from the ordering causes effects similar to the folding of the Brillouin zone, although phonon intensities at new Brillouin zone centres are weak. The coupling of low-energy phonon modes with displacement of mobile ions can explain the strong damping of phonons at q > 0.5 observed in the experiment.

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“…This property has been recognized as the low energy excitations in the field of superionic conductors [28][29][30][31]. The flat phonon band implies that many phonon modes have almost the same energy.…”

Section: Discussionmentioning

confidence: 99%