Influence of the cation disordering on the electronic conductivity of superionic copper selenide

Temperature-dependent conductivity of Emim+ (Emim+ = 1-ethyl-3-methyl imidazolium) confined in channels of a metal–organic framework

“…Before the phase temperature, due to the increase in the temperature leading to the increase of the disorder of the Emim + cation, the concentration of the Emim + cation charge in the channel would decrease. 19 As a result, the conductivity of 1 decreases with the increase in the temperature, as demonstrated in the previous work. 19 After the phase transition, however, owing to the increase in the temperature leading to the increase of the orientation order and motion of the Emim + cations, the concentration of the Emim + cation charge and the mobility of the cations in the channel would increase, leading to the conductivity of 1 increasing with the increase in the temperature.…”

“…19 As a result, the conductivity of 1 decreases with the increase in the temperature, as demonstrated in the previous work. 19 After the phase transition, however, owing to the increase in the temperature leading to the increase of the orientation order and motion of the Emim + cations, the concentration of the Emim + cation charge and the mobility of the cations in the channel would increase, leading to the conductivity of 1 increasing with the increase in the temperature. This deduction is not only very consistent with the temperature-dependent conductivity of 1, but also demonstrated by the temperature-dependent dielectric loss (tand), since the dielectric loss (tand) is an indication of leakage current in 1.…”

Solving the disordered structure of β-Cu2−xSe using the three-dimensional difference pair distribution function

“…Cu 2Àx Se is a promising thermoelectric material as it is cheap, non-toxic and has a high thermoelectric figure of merit (zT) (Eikeland et al, 2017;Liu, Yuan et al, 2013;Lu et al, 2015;Qiu et al, 2016;Nguyen et al, 2013;Brown et al, 2016;Brown, Day, Caillat & Snyder, 2013;Brown, Day, Borup et al, 2013;Dalgaard et al, 2018;Liu et al, 2012;Miyatani, 1973;Vučić et al, 1984Vučić et al, , 1981Vucic et al, 1982;Yu et al, 2012;Chi et al, 2014;Mahan, 2015;Sirusi et al, 2015;Sun et al, 2015;Kang et al, 2016). The compound has a phase transition at 350-410 K depending on the degree of Cu deficiency (Brown, Day, Caillat & Snyder, 2013;Chi et al, 2014;Eikeland et al, 2017;Liu, Yuan et al, 2013;Vučić et al, 1984).…”

“…The compound has a phase transition at 350-410 K depending on the degree of Cu deficiency (Brown, Day, Caillat, et al, 2013;Chi et al, 2014;Eikeland et al, 2017;Liu, Yuan, et al, 2013;Vučić et al, 1984). Both low-and high-temperature phases have been studied for their thermoelectric properties, while the high-temperature phase is also a superionic conductor (Miyatani, 1973;Vucic et al, 1982;Mahan, 2015;Sirusi et al, 2015;Stephen Dongmin et al, 2016). The compound has been described as a phonon-liquid electron-crystal material due to its good electrical conductivity and low thermal conductivity (Liu et al, 2012).…”

Apparent critical phenomena in the superionic phase transition of Cu2-xSe

“…These points altogether suggests that the transport property behavior at the Cu Se superionic phase transition should be explained with a discontinuous transition picture rather than with critical fluctuations. In light of this understanding, we refer to the drastic changes associated with the phase transition as [8,9,11,12] all report a nominal composition of Cu Se 2 unless otherwise specified. All data from this study are measured upon heating.…”