Universal Approach for Scaling the ac Conductivity in Ionic Glasses

Sidebottom, David L.

doi:10.1103/physrevlett.82.3653

Cited by 296 publications

(219 citation statements)

References 18 publications

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“…The apparent universality of conduction in disordered solids has been discussed by Dyre and Schrøder who suggested various macroscopic and microscopic models that predict such universality in the extreme disorder limit [3]. Since universality is an idealized concept, it is not surprising that most claims for universal behavior and models [e.g., 4,5] have been found too limited or even incorrect, but this should not discourage new universality proposals, ones that are generally doomed eventually to suffer the same fate as new experimental results are analyzed and the domain to which the model is applied is sufficiently extended.…”

Section: Introductionmentioning

confidence: 99%

Universality, the Barton Nakajima Namikawa relation, and scaling for dispersive ionic materials

Macdonald

2005

Phys. Rev. B

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Many frequency-response analyses of experimental data for homogeneous glasses and single-crystals involving mobile ions of a single type indicate that estimates of the stretchedexponential 1 β shape parameter of the Kohlrausch K1 fitting model are close to 1/3 and are virtually independent of both temperature and ionic concentration. This model, which usually yields better fits than others, is indirectly associated with temporal-domain stretched-exponential response having the same 1 β parameter value. Here it is shown that for the above conditions several different analyses yield the important and unique value of exactly 1/3 for the 1 β of the K1 model. It is therefore appropriate to fix the 1 β parameter of this model at the constant value of 1/3, then defined as the U model. It fits data sets exhibiting conductive-system dispersion that vary with both temperature and concentration just as well as those with 1 β free to vary, and it leads to a correspondingly universal value of the Barton-Nakajima-Namikawa (BNN) parameter p of 1.65.Composite-model complex-nonlinear-least-squares fitting, including the dispersive U-model, the effects of the bulk dipolar-electronic dielectric constant, D

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Section: Introductionmentioning

confidence: 99%

Universality, the Barton Nakajima Namikawa relation, and scaling for dispersive ionic materials

Macdonald

2005

Phys. Rev. B

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“…DOI: 10.1103/PhysRevLett.86.1279 Much effort has been devoted during the last few decades to understand the dynamics of ionic transport in ionically conducting materials. In spite of the advances made, there is still no general agreement on interpretation of the experimental data [1][2][3][4][5][6][7][8][9][10][11]. Most research activity in this field has focused on the origin and properties of the long-range ion motion, and electrical relaxation is the most commonly used experimental tool to access the ion dynamics.…”

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confidence: 99%

Origin of Constant Loss in Ionic Conductors

et al. 2001

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We have analyzed the constant loss contribution to the ac conductivity in the frequency range 10 Hz -1 MHz and temperatures down to 8 K, for two Li ionic conductors, one crystalline (Li 0.18 La 0.61 TiO 3 ) and the other glassy (61SiO 2 ? 35Li 2 O ? 3Al 2 O 3 ? P 2 O 5 ). As temperature is increased a crossover is observed from a nearly constant loss to a fractional power law frequency dependence of the ac conductivity. At any fixed frequency v, this crossover occurs at a temperature T such that v ഠ n 0 exp͑2E m ͞k B T͒, where n 0 is the attempt frequency and E m is identified with the barrier for Li 1 ions to leave their wells. DOI: 10.1103/PhysRevLett.86.1279 Much effort has been devoted during the last few decades to understand the dynamics of ionic transport in ionically conducting materials. In spite of the advances made, there is still no general agreement on interpretation of the experimental data [1][2][3][4][5][6][7][8][9][10][11]. Most research activity in this field has focused on the origin and properties of the long-range ion motion, and electrical relaxation is the most commonly used experimental tool to access the ion dynamics. The frequency dependence of the ionic conductivity can be usually well described by using Jonscher's expression [12]where s 0 is the dc conductivity, v p is a characteristic relaxation frequency, and n is a fractional exponent. Both s 0 and v p are thermally activated with about the same activation energy, indicating that the dispersive conductivity, s ‫ء‬ ͑v͒, originates from migration of ions. However, there is another ubiquitous contribution to dispersive conductivity that has received much less attention so far. This contribution consists of a nearly frequency independent dielectric loss,´0 0 ͑v͒ ഠ A, which corresponds to an almost linear frequency dependent term of the form s 0 ͑v͒ v´0 0 ͑v͒ ഠ Av in the real part of the complex conductivity. At sufficiently low temperature or high frequencies, the Av term dominates over the power law dependence of exponent n. The existence of this nearly constant loss (NCL) was suggested more than 20 years ago and subsequently verified [13,14]. Since then, few investigations of its properties have been made [15][16][17] and low temperature data with its dominant contribution are still scarce.Although, ultimately, mobile ions seem to be responsible also for the NCL, the experimental facts including its dependence on temperature and the effect of mixed alkalis point to a different origin than ionic hopping [18]. Experimentally, A is not thermally activated and has temperature dependence much milder than s 0 or v p [18][19][20]. Partial replacement by alkali ions of a different kind has the effect of reducing the NCL [3,18,21,22], but the reduction in A is much smaller than the decrease in s 0 due to the well-known mixed alkali effect [3]. From these facts, it has been very recently proposed [18] that local vibrational relaxation reflected in the mean-square displacement of ions could be the origin of the constant loss in ionic conductors...

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“…The variation of s with temperature for a variety of disordered materials was extensively analyzed in the past and is shown to be critically dependent on the ac conduction mechanism [20][21][22][23][24][25]. For example, in cases where the conductivity is believed to be due to phonon-assisted tunneling between defect states, or the so-called quantum-mechanical tunneling (QMT) phenomena, the ac conductivity σ (ω) takes the functional form [18,[20][21][22][23][24][25][26][27][28] …”

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confidence: 99%

“…Therefore, understanding the correlation between the structure and physical properties of these materials is of fundamental interest. In particular, studying the electrical conduction mechanisms [20][21][22][23][24][25][26][27][28] of 2D layered solids is of major importance, since it would play a relevant role in many of the envisioned optoelectronic applications based on these materials.…”

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confidence: 99%

Universal ac conduction in large area atomic layers of CVD-grown MoS2

et al. 2014

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Here, we report on the ac conductivity [σ (ω); 10 mHz < ω < 0.1 MHz] measurements performed on atomically thin, two-dimensional layers of MoS 2 grown by chemical vapor deposition (CVD). σ (ω) is observed to display a "universal" power law, i.e., σ (ω) ∼ ω s measured within a broad range of temperatures, 10 K < T < 340 K. The temperature dependence of ''s" indicates that the dominant ac transport conduction mechanism in CVD-grown MoS 2 is due to electron hopping through a quantum mechanical tunneling process. The ac conductivity also displays scaling behavior, which leads to the collapse of the ac conductivity curves obtained at various temperatures into a single master curve. These findings establish a basis for our understanding of the transport mechanism in atomically thin, CVD-grown MoS 2 layers.

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Universal Approach for Scaling the ac Conductivity in Ionic Glasses

Cited by 296 publications

References 18 publications

Universality, the Barton Nakajima Namikawa relation, and scaling for dispersive ionic materials

Universality, the Barton Nakajima Namikawa relation, and scaling for dispersive ionic materials

Origin of Constant Loss in Ionic Conductors

Universal ac conduction in large area atomic layers of CVD-grown MoS2

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