Observation of characteristic phonon spectra for cage and mobile ions in the layered superionic conductor AgCrS2

Ion conduction in proton- and related defect (super) ionic conductors: Mechanical, electronic and structure parameters

“…1-4 with Eqs. (10), (14), (15), (18) and (19) may justify quantitatively the conduction mechanism proposed qualitatively by Wakamura [11], that is based on the ion hopping assisted by enhanced vibration displacement of the host lattice mode, common in various kinds of conduction elements. It is characterized with specific electronic structure near the band gap, heavy atomic mass of the constituent ion, expansion of volume of unit cell, and the long-range periodicity of crystal structure.…”

“…The second is a broadened band shape observed in many IHCs [17,[35][36][37]57], SPCs [39,[70][71][72][73], β-alumina [40,41,74], Li-ion conductors [2,42], YSZ [43,59,60], and NdGaO 3 [75], and also rapid band broadening of the host lattice mode with increasing temperature observed in SICs [8][9][10][11]15,34,76]. Both the behaviors are typical evidence for the fourth-order anharmonicity.…”

“…For the E ac value of LiN 2 H 5 SO 4 , we employ the value measured by Kreuer et al [32], instead of 0.07 eV assigned by Frech and Brown, since they obtained it from the half width of the vibration mode without taking the fourth-order term [33], in spite of considerable magnitude of that term as predicted from SICs [8][9][10]34] and IHCs [35][36][37][38]. 7) or Eq.…”

“…For SICs, Brüesch et al considered the coupling of shear-type vibration mode with movable ion [8]. Wakamura et al noticed close relation of the phonon frequency of optical mode to E ac value [9,10], and understood it qualitatively from double minimum potential produced with the third-and fourth-order phonon-phonon couplings [11].…”

“…For those conductors, significant relations of the vibration modes and of the electronic energy state near the band gap on conduction ion have been discussed by several researchers [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. For SICs, Brüesch et al considered the coupling of shear-type vibration mode with movable ion [8].…”