Thermoelectrics, which can generate electricity from a temperature difference, or vice versa, is a key technology for solid‐state cooling and energy harvesting; however, its applications are ...constrained owing to low efficiency. Since the conversion efficiency of thermoelectric devices is directly obtained via a figure of merit of materials, zT, which is related to the electronic and thermal transport characteristics, the aim here is to elucidate physical parameters that should be considered to understand transport phenomena in semiconducting materials. It is found that the weighted mobility ratio of the majority and minority carrier bands is an important parameter that determines zT. For nanograined Bi–Sb–Te alloy, the unremarked role of this parameter on temperature‐dependent electronic transport properties is demonstrated. This analysis shows that the control of the weighted mobility ratio is a promising way to enhance zT of narrow bandgap thermoelectric materials.
Suppression of the bipolar conduction in narrow‐bandgap thermoelectric materials is crucial for improving their device efficiency. This work correlates the weighted mobility ratio in thermoelectric figure of merit and bipolar conduction in bismuth‐telluride‐based alloys. The results suggest that increasing the weighted mobility ratio suppresses the bipolar conduction most effectively among other parameters like carrier concentration and bandgap.
A
bstract
We investigate the properties of pole-skipping of the sound channel in which the translational symmetry is broken explicitly or spontaneously. For this purpose, we analyze, in detail, not ...only the holographic axion model, but also the magnetically charged black holes with two methods: the near-horizon analysis and quasi-normal mode computations. We find that the pole-skipping points are related with the chaotic properties, Lyapunov exponent (
λ
L
) and butterfly velocity (
v
B
), independently of the symmetry breaking patterns. We show that the diffusion constant (
D
) is bounded by
D
≥
v
B
2
/
λ
L
, where
D
is the energy diffusion (crystal diffusion) bound for explicit (spontaneous) symmetry breaking. We confirm that the lower bound is obtained by the pole-skipping analysis in the low temperature limit.
Band engineering is an effective strategy to improve the electronic transport properties of semiconductors. In thermoelectric materials research, density‐of‐states effective mass is an undoubted key ...factor in verifying the band engineering effect and establishing a strategy for enhancing thermoelectric performance. However, estimation of the effective mass is demanding or inaccurate depending on the methods taken. A simple equation is proposed, valid for all degeneracy: Log10 (md*T/300) = (2/3) Log10 (n) − (2/3) 20.3 − (0.00508 × |S|) + (1.58 × 0.967|S|) that utilizes experimentally determined Seebeck coefficient (S) and carrier concentration (n) to determine the effective mass (md*) at a temperature (T). This straightforward equation, which gives an accurate analysis of the band modulation in terms of md*, is indispensable in designing thermoelectric materials of maximized performance.
The density‐of‐states (DOS) effective mass of thermoelectric materials can be estimated accurately with the single parabolic band model. However due to complex Fermi integral calculations involved, an equation that is valid in degenerate materials is instead utilized erroneously. This work proposes another simple, universal, and accurate equation that can be used for any degeneracy to determine the DOS effective mass.
Filled skutterudites R(x)Co4Sb12 are excellent n-type thermoelectric materials owing to their high electronic mobility and high effective mass, combined with low thermal conductivity associated with ...the addition of filler atoms into the void site. The favourable electronic band structure in n-type CoSb3 is typically attributed to threefold degeneracy at the conduction band minimum accompanied by linear band behaviour at higher carrier concentrations, which is thought to be related to the increase in effective mass as the doping level increases. Using combined experimental and computational studies, we show instead that a secondary conduction band with 12 conducting carrier pockets (which converges with the primary band at high temperatures) is responsible for the extraordinary thermoelectric performance of n-type CoSb3 skutterudites. A theoretical explanation is also provided as to why the linear (or Kane-type) band feature is not beneficial for thermoelectrics.
A
bstract
We study the holographic duality between the reflected entropy and the entanglement wedge cross section with the first order correction. In the field theory side, we consider the reflected ...entropy for
ρ
AB
m
, where
ρ
AB
is the reduced density matrix for two intervals in the ground state. The reflected entropy in the 2d holographic conformal field theories is computed perturbatively up to the first order in
m −
1 by using the semiclassical conformal block. In the gravity side, we compute the entanglement wedge cross section in the backreacted geometry by cosmic branes with tension
T
m
which are anchored at the AdS boundary. Comparing both results we find a perfect agreement, showing the duality works with the first order correction in
m −
1.
In analyzing zT improvements due to lattice thermal conductivity (κL) reduction, electrical conductivity (σ) and total thermal conductivity (κTotal) are often used to estimate the electronic ...component of the thermal conductivity (κE) and in turn κL from κL = ∼ κTotal − LσT. The Wiedemann-Franz law, κE = LσT, where L is Lorenz number, is widely used to estimate κE from σ measurements. It is a common practice to treat L as a universal factor with 2.44 × 10−8 WΩK−2 (degenerate limit). However, significant deviations from the degenerate limit (approximately 40% or more for Kane bands) are known to occur for non-degenerate semiconductors where L converges to 1.5 × 10−8 WΩK−2 for acoustic phonon scattering. The decrease in L is correlated with an increase in thermopower (absolute value of Seebeck coefficient (S)). Thus, a first order correction to the degenerate limit of L can be based on the measured thermopower, |S|, independent of temperature or doping. We propose the equation: L=1.5+exp−|S|116 (where L is in 10−8 WΩK−2 and S in μV/K) as a satisfactory approximation for L. This equation is accurate within 5% for single parabolic band/acoustic phonon scattering assumption and within 20% for PbSe, PbS, PbTe, Si0.8Ge0.2 where more complexity is introduced, such as non-parabolic Kane bands, multiple bands, and/or alternate scattering mechanisms. The use of this equation for L rather than a constant value (when detailed band structure and scattering mechanism is not known) will significantly improve the estimation of lattice thermal conductivity.
Bi2Te3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by ...optimizing the converging valence bands of Bi2Te3 and Sb2Te3 in the (Bi1−xSbx)2Te3 system when x=0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi0.25Sb0.75)2Te3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT=1.05 (at 300K) without nanostructuring.
In this article, I propose a three-stage estimation model to examine the effect of parental divorce on the development of children's cognitive skills and noncognitive traits. Using a framework that ...includes pre-, in-, and post-divorce time periods, I disentangle the complex factors affecting children of divorce. I use the Early Childhood Longitudinal Study-Kindergarten Class 1998 to 1999 (ECLS-K), a multiwave longitudinal dataset, to assess the three-stage model. To evaluate the parameters of interest more rigorously, I employ a stage-specific ordinary least squares (OLS) model, a counterfactual matching estimator, and a piece-wise growth curve model. Within some combinations of developmental domains and stages, in particular from the in-divorce stage onward, I find negative effects of divorce even after accounting for selection factors that influence children's skills and traits at or before the beginning of the dissolution process. These negative outcomes do not appear to intensify or abate in the ensuing study period.
Purpose
Creating superior customer experience quality is important to firm success, but the link between customer experience quality and customer-to-customer interaction quality – a critical ...component of customer experience quality in mass service settings – has seldom been spotlighted. This paper aims to propose and test a theoretical model of the relationship among three types of customer-to-customer interaction quality (friend-interaction, neighboring customer-interaction and audience-interaction) and customer experience quality. They also examine these variables’ effects on customer citizenship behavior in mass service settings.
Design/methodology/approach
The authors collected data through a self-administered survey. The proposed relationships were tested using structural equation modeling.
Findings
Friend-interaction and audience-interaction quality perceptions significantly influence customer experience quality, with neighboring customer-interaction quality perception significant only for low communication quality. We find that enhancing customer experience quality is crucial to promoting citizenship behavior in mass service settings.
Practical implications
Neighboring customer-interaction quality perception has a significant effect on customer experience quality, particularly in a low communication quality situation. Therefore, service marketers should provide effective neighboring customer-interaction management schemes to enhance experience quality together with friend-interaction and audience-interaction management schemes when customers experience low communication quality. Additionally, service marketers should focus on enhancing communication quality only when anticipating low neighboring customer-interaction quality.
Originality/value
The findings highlight the effects of three types of customer-to-customer interaction quality on customer citizenship behavior through experience quality perception in mass service settings, and the effect of neighboring customer-interaction quality perception on customer experience quality, moderated by communication quality.
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