Local Lattice Structure Research Articles

Revealing the Interplay of Local Environments and Ionic Transport in Perovskite Solid Electrolytes.

Solid-state ionic conduction is significantly influenced by bottleneck sizes, which impede ion diffusion within solid lattices. Using aberration-corrected scanning transmission electron microscopy and multislice electron ptychography, we directly observed that increased La occupancy in the perovskite solid electrolyte Li0.5La0.5TiO3 correlates with reduced bottleneck sizes formed by four oxygen atoms connecting neighboring A-site cages. This correlation was also confirmed in local aperiodic regions, where smaller bottleneck sizes due to increased La occupancies affect the directionality and dimensionality of the Li+ ion conductivity. Furthermore, while prior studies have focused on averaged Li+ ion diffusion across different bottleneck areas or chemical environments, by devising a molecular dynamics (MD)-based methodology, we quantify the diffusivity of Li+ ions through specific bottleneck regions. Atomistic simulations, including nudged elastic band calculations and this MD-based methodology, revealed that larger bottleneck sizes correlate with smaller local migration barriers and higher local diffusivity. This study elucidates the relationship among local chemistry, lattice structure, and Li+ ion transport, providing insights for the design of advanced oxide solid electrolytes.

Highly Diffusive Nonluminescent Carriers in Hybrid Phase Lead Triiodide Perovskite Nanowires

AbstractCrystal structural rearrangements unavoidably introduce defects into materials, where even these small changes in local lattice structure could arouse a prominent impact on the overall nature of crystals. Contrary to the traditional notion that defects obstruct carrier transport, herein, we report a promoted transport mechanism of nonluminescent carriers in single‐crystalline CH3NH3PbI3 nanowires (1345.2 cm2 V−1 s−1, about a 14‐fold improvement), enabled by the phase transition induced defects (PTIDs). Carriers captured by PTIDs evade both the radiative and non‐radiative recombinations during the incomplete tetragonal‐to‐orthorhombic phase transition at low temperatures, forming a specific nonluminescent state that exhibits an efficient long‐distance transport and thereby realize a prominent enhancement of photocurrent responsivity for photodetector applications. The findings provide broader insights into the carrier transport mechanism in perovskite semiconductors and have significant implications for their rational design for photoelectronic applications at varied operating temperatures.

Highly Diffusive Nonluminescent Carriers in Hybrid Phase Lead Triiodide Perovskite Nanowires.

Crystal structural rearrangements unavoidably introduce defects into materials, where even these small changes in local lattice structure could arouse a prominent impact on the overall nature of crystals. Contrary to the traditional notion that defects obstruct carrier transport, herein, we report a promoted transport mechanism of nonluminescent carriers in single-crystalline CH3NH3PbI3 nanowires (1345.2 cm2 V-1 s-1, about a 14-fold improvement), enabled by the phase transition induced defects (PTIDs). Carriers captured by PTIDs evade both the radiative and non-radiative recombinations during the incomplete tetragonal-to-orthorhombic phase transition at low temperatures, forming a specific nonluminescent state that exhibits an efficient long-distance transport and thereby realize a prominent enhancement of photocurrent responsivity for photodetector applications. The findings provide broader insights into the carrier transport mechanism in perovskite semiconductors and have significant implications for their rational design for photoelectronic applications at varied operating temperatures.

Investigation of the sintering behavior of nanoparticulate SiC by molecular dynamics simulation

Sintering is a valuable processing technique utilized to create bulk materials from powder compacts. In recent years, sintering has a garnered significant attention in the research community due to its versatility and applicability in various fields, including additive manufacturing. Herein, we investigate the sintering kinetics and mechanism of SiC nanoparticulate using molecular dynamics simulations. The surface morphology, microstructure, radial distribution function, mean square displacement, atomic displacement distribution, structural transformation, and diffusion coefficient are analyzed in detail. The free surface surrounding the neck undergoes a reconstruction to eventually reach an equilibrium dihedral angle. The neck rapidly grows and aligns with the surface, causing the SiC particle to transform from an original spherical shape into a twists shape. The concentration of shear stress results in a change of the local lattice structure from the face-centered cubic phase to amorphous phase in the surface. With an increasing sintering time, the dominant diffusion mechanism gradually shifts from surface diffusion to interface diffusion. This trend leads to a rise in the atomic migration, the consumption of interface energy, and the degree of particle fusion. Ultimately, the sintered SiC particles have the spherical shape, low surface energy, and stable structure. Additionally, the high mobility of melted atom causes a gradual dissolution of SiC particle into the large particle from the surface towards the interior. This process leads to high-altitude concentration structures that facilitate atomic migration. These results shed light on an atomic sintering mechanism in SiC nanoparticulate for applications in the preparation of nanostructured materials, and additive manufacturing.

The Effect of Structural Disorder on Li-Ion Transport in the Inorganic Components of the Electrode-Electrolyte Interfaces of Li-Ion Batteries

Conventional organic electrolytes in Li-ion batteries have an electrochemical window that is too narrow, leading to a decomposition at the cathode and anode surfaces, especially at high voltages. The breakdown of the electrolyte leads to the formation of cathode-electrolyte interphase (CEI) and solid-electrolyte interface (SEI) at the anode. These interfaces are a multicomponent, 3-dimensional heterogeneous structures that span from a few nanometers to micrometers. To understand the atomic-scale impact of the interfaces’ structure and chemistry on function we have run molecular dynamics simulations of the Li-ion diffusivity in the most likely components: LiF, Li2CO3, and Li2O. Our work focuses on identifying the effect of local chemistry and lattice structure in disordered or amorphous component materials on Li-diffusivity. We extract Li-ion diffusivity and the activation energy for Li-ion transport from both machine learning force fields and ab-initio molecular dynamics from the individual components of the interface and explicit interfaces. Post analysis establishes the local correlation between atomic structure, chemistry, and Li-ion migration. If well designed, the SEI and CEI can protect the electrolyte and cathode to prevent further degradation during cycling and thus optimization of battery performance.This work was sponsored by the Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office and was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Unlocking Chlorine Oxide‐Based Ultra‐Wideband Near‐Infrared Phosphor and Advancing Spectral Performance via Lattice Engineering

AbstractNear‐infrared (NIR) phosphor‐converted light–emitting diodes (pc‐LEDs) are increasingly used in night vision, surveillance, and biomedicine. A major challenge is to identify a phosphor that efficiently converts blue light into wideband NIR emission. In this paper, a rare‐earth divalent europium (Eu2+)‐activated halogen oxide (Sr3GeO4Cl2) phosphor is unlocked via a high‐temperature solid‐state reaction. The Sr3GeO4Cl2:Eu2+ phosphor emits a wide spectrum (500–950 nm) with a peak at 700 nm when excited by 450 nm blue light. Extended X‐ray absorption fine structure (EXAFS) analysis reveals that the NIR emission primarily originates from Eu2+ ions, and the Eu─O bond length closely resembles the Sr─O bond length. Lattice engineering, specifically Ge/Si cation substitution, increased Eu2+ incorporation into the crystal lattice, boosting luminescence intensity by 75%–122% and quantum efficiency from 15% to 26%. This is related to the combined effect of reduced non‐radiative energy transfer and changes in the local lattice structure of Eu2+. A NIR pc‐LED device using the optimized phosphor showed a photoelectric efficiency of 16.5% and an optical output of 25.07 mW at 100 mA. This study not only explores new Eu2+‐activated NIR phosphors but also highlights the importance of crystal engineering to enhance luminescence properties, guiding future research for efficient NIR pc‐LED development.

Atomic thermal fluctuation reduction method for robust local lattice structure identification in finite-temperature molecular dynamics

Classical molecular dynamics (MD) is extensively employed to explore the properties, deformations, and fractures of materials at the atomic scale. Identifying local structures is crucial for understanding the mechanisms behind material deformation and fracture. Nevertheless, analyzing the local lattice structure at high temperatures poses challenges due to atomic thermal fluctuations, which act as noise and potentially lead to misjudgment of the local lattice structure. To date, various strategies have been implemented to circumvent this issue. However, they cannot be a solution because it is unable to reproduce phenomena unique to high temperatures, whereas others require significant computational resources. This paper introduces an innovative method to reduce atomic thermal fluctuations using a straightforward algorithm, thereby facilitating accurate identification of local lattice structures even at high temperatures. Our approach incorporates novel degrees of freedom, termed ‘Markers,’ that are linked to atoms. By reducing the thermal fluctuation of these Markers, precise analysis of the local lattice structure becomes feasible. The efficacy of this method is validated through its thermal reducibility and Markers trackabilities to atoms. Utilizing common neighbor analysis, the error rate for structure identification with our method is nearly 0% at temperatures up to 1200 K in Fe, in contrast to approximately 5% without it. Furthermore, the average distance between atoms and Markers remains below 0.1 Å. Applying our method to phase transformations, we successfully observed the transition from face-centered cubic to body-centered cubic structure in Fe at 1200 K. This method holds promise for expanding the capabilities of MD simulations at high temperatures.

Understanding the electrochemical properties of Mg-doped Li2MnO3: first-principles calculations.

Non-transition metal doping, especially for Mg, has been gradually employed to optimize the electrochemical performance of Li-rich cathode material Li2MnO3. However, the effects of Mg doping on the electrochemical behavior of Li2MnO3 have not been studied extensively. In this work, we investigate the effect of Mg doping at both the 2b (in the Li/Mn mixed layer) and 4h (in the Li layer) Li sites on the electrochemical properties of Li2MnO3 through first-principles calculations and ab initio molecular dynamics simulations. The local lattice structure, electronic density of states, Bader charge, delithiation voltage, lattice oxygen stability and Li diffusion kinetics are examined. Electronic structure analysis shows that Mg can activate the electrochemical activity of surrounding Mn by charge transfer, making Mn participate in charge compensation at the initial delithiation stage. Mg doping can also cause an increase in the average oxygen vacancy formation energy and hence depress the oxygen release during the delithiation process. Molecular dynamics simulations show that the diffusion kinetics of Li ions in Mg2b-Li2MnO3 is enhanced with respect to the undoped one, whereas Mg doped at the 4h site cannot improve the diffusion kinetics of Li ions. Further studies found that Mg doped at the 2b site results in a decrease in the energy barrier for the intra-layer diffusion and an increase in the energy barrier for the inter-layer diffusion of the nearby Li vacancies.

Advanced Analytical Electron Microscopy Techniques for Probing Individual PGM-Free Catalyst Sites

Hydrogen fuel cells currently utilize expensive platinum group metal nanoparticles as catalysts [1]. To reduce the cost of catalyst materials, large efforts to develop viable platinum group metal-free (PGM-free) catalyst materials, which often consist of single transition metal atoms embedded in nitrogen-doped graphitic carbon structures, are being undertaken [2]. Given the atomic-scale nature of the metal sites in these materials, their performance and stability are highly dependent on the local coordination environment and consequently electronic structure of the sites [3]. A detailed understanding of the local elemental composition and lattice structure of individual sites, and how these properties vary between sites, is therefore needed to further develop improved PGM-free catalyst materials. While many bulk techniques are available that can provide average properties of these sites, such as Mössbauer and X-ray absorption spectroscopies, techniques with high spatial resolution are needed to measure the properties of individual sites. As a result, scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS) has proven an invaluable tool for characterization of these materials due to its ability to probe structural and electronic properties at the atomic scale [4]. However, combined with the instability of many metal sites under the electron probe, the quantity and type of information accessible by conventional STEM instrumentation and acquisition methods is limited. To better understand the local coordination environment and electronic structure of individual sites, as well as how these properties vary site to site, new techniques and hardware are therefore needed.Here, we demonstrate advancements in STEM-EELS and -EDS that allow the quality and quantity of spectroscopic information obtained from individual sites to be significantly improved over conventional method. First, we demonstrate direct real-space mapping of metal sites by using a direct electron detector in the EELS spectrometer. This increases the data acquisition rate and signal-to-noise ratio sufficiently to map metal atom positions at the atomic scale. In addition, we show how automated metal atom position identification and subsequent probe positioning allow the rate at which metal sites are probed to be increased by another order of magnitude while simultaneously increasing the quantity of data obtained from each site. Using EELS and EDS signals acquired in parallel, this automated acquisition method enables a wide range of metal site elements to be identified, as well as the local coordination environment around the sites to be determined. Combined with electronic structure measurements of the metal atoms themselves, this technique provides significantly more information about individual sites than conventional methods. The techniques presented here are therefore poised to significantly improve our understanding of the local coordination environment and electronic structure of individual PGM-free metal sites, as well how these properties vary site to site, accelerating development of these low-cost hydrogen fuel cell catalyst materials [5].

Multifrequency EPR spectroscopy study of Mn, Fe, and Cu doped nanocrystalline ZnO

Mn, Fe, and Cu ions, when doped into ZnO nanocrystals, impart magnetic phenomena to their semiconducting property. Although notable in the dilute magnetic semiconductor community, transition metal (TM) ion-doped ZnO lacks investigations that inform researchers on the local lattice structure around the dopant ion, its spin-exchange phenomena, and the interaction between its intrinsic defects and the doped metal ion. The current study presents a detailed multi-frequency (X- and Q-band) EPR investigation that clarifies the localization of the dopant ion, its site symmetry, and the formation of intrinsic-extrinsic defect complexes in ZnO:TM. The incorporation of TM ion is observed to modify the intrinsic defect structure of ZnO nanocrystals. Particularly, a deviation from the core-shell model is observed for ZnO:TM, and the appearance of intrinsic-extrinsic defect complexes that may contribute to a peculiar spin-exchange phenomenon are noticed. Additionally, the localization as observed from the resonance lines of defect complexes comprising Cu2+ is different from those of Mn2+ and Fe3+, showing charge selective substitutions in the matrix.

Impacts of the Lattice Strain on Perovskite Light‐Emitting Diodes

AbstractThe development of perovskite light‐emitting diodes (PeLEDs) with both high efficiency and excellent stability remains challenging. Herein, a strong correlation between the lattice strain in perovskite films and the stability of resulting PeLEDs is revealed. Based on high‐efficiency PeLEDs, the device lifetime is optimized by rationally tailoring the lattice strain in perovskite films. A PeLED with a high peak external quantum efficiency of 18.2% and a long lifetime of 151 h (T70, under a current density of 20 mA cm−2) is realized with a minimized lattice strain in the perovskite film. In addition, an increase in the lattice strain is found during the long‐time device stability test, indicating that the degradation of the local perovskite lattice structure could be one of the degradation mechanisms for long‐term stable PeLEDs.

Giant and Controllable Photoplasticity and Photoelasticity in Compound Semiconductors.

We show that the wide-band gap compound semiconductors ZnO, ZnS, and CdS feature large photoplastic and photoelastic effects that are mediated by point defects. We measure the mechanical properties of ceramics and single crystals using nanoindentation, and we find that elasticity and plasticity vary strongly with moderate illumination. For instance, the elastic stiffness of ZnO can increase by greater than 40% due to blue illumination of intensity 1.4 mW/cm^{2}. Above-band-gap illumination (e.g., uv light) has the strongest effect, and the relative effect of subband gap illumination varies between samples-a clear sign of defect-mediated processes. We show giant optomechanical effects can be tuned by materials processing, and that processing dependence can be understood within a framework of point defect equilibrium. The photoplastic effect can be understood by a long-established theory of charged dislocation motion. The photoelastic effect requires a new theoretical framework which we present using density functional theory to study the effect of point defect ionization on local lattice structure and elastic tensors. Our results update the longstanding but lesser-studied field of semiconductor optomechanics, and suggest interesting applications.

Effects of local lattice deformation on magnetic anisotropy of W-type ferrites

We calculate the magnetic anisotropy (MA) energy of W-type ferrites, Ba(Sr)Me2Fe16O27, where Me is Mg, Co, and Ni, using a cluster model and LS coupling on magnetic ions, along with the structural data obtained via x-ray and neutron diffractions. We show that the local MA energy of Fe3＋ and Me2+ on each non-equivalent site depends strongly on the local lattice structure around the magnetic ions. The bulk MA energy calculated for W-type ferrite with Me=Mg is found to be weakly dependent on the details of local lattice structures, and the calculated result is consistent with that observed for SrMg 2Fe16O27. Results for W-type ferrite with Me=Co suggest the appearance of a cone-type magnetic structure; however, c− plane MA may appear when a small amount of Co2+ resides on 12k sites. The finding could resolve the experimental controversy for the magnetic structure of W-type ferrite with Me=Co. Based on the results, we discuss site-selective substitution of Me2+ (Me = Fe, Co, and Ni) to enhance the performance of permanent magnets.

Visualization and control of oxygen dopant ordering in a cuprate superconductor

A proper amount of excess oxygen plays a significant role in hole-doped cuprate high-Tc superconductivity. Here, we directly resolve the interstitial oxygen atoms are located in the spacer La2O2+δ layers of La2CuO4+δ superconductors via integrated differential phase contrast (iDPC) technique. The distribution of dopant oxygen in La2CuO4+δ is observed to be related with local strain states. Induced large in-plane stress in the La2CuO4+δ film forms periodic alternating tensile and compressive strain in the La–O layers. The mobile interstitial oxygen dopants get self-organized, instead of randomly distributed, to form oxygen-depleted stripes separated by ordered oxygen interstitials. The influence of dopant oxygen on the local atomic lattice and electronic structure was further examined by density functional theory (DFT) calculations. The interplay between the interstitial oxygen dopants and the CuO6 octahedra not only accommodates the distortions of the local atomic arrangement but also alters the electronic states by transferring charge from the LaO planes to the CuO2 planes. Our results may also be applicable to other oxygen-doped cuprates with high-Tc superconductivity.

Bimodal Plasmonic Color Filters Enable Direct Optical Imaging of Ion Implantation in Thin Films (Adv. Funct. Mater. 3/2022)

Ion Implantation In article number 2009419, Eugeniu Balaur, Brian Abbey, and Catherine Sadatnajafi present a new approach to characterise the effects of ion implantation in ultra-thin films. The plasmon resonances generated by optically active metamaterials can be used to probe minute changes in the local lattice structure, which varies as a function of the dopant density.

Lattice defects related magnetic and magnetocapacitance properties of multiferroic BaFe10.2Sc1.8O19 epitaxial thin films

Without changing the crystalline structure of BaFe10.2Sc1.8O19 (BFSO) epitaxial thin film, significant modulation of its saturation magnetization (from 75 to 180 emu/cc), magnetic anisotropy field (from 3590 to 1434 Oe) and multiferroic ordering temperature (from 207 to 306 K) can be realized with different densities of lattice defects (DLD). A defects-related effective magnetic field Heff is defined. Heff reduces obviously with increasing annealing temperature TA, agreeing well with the reduced DLD. The defects-related magnetic ordering of BFSO films is further verified in the magnetocapacitance devices. The magnetocapacitance for 1000 °C annealed film is more than 5 times larger than that of as-deposited film. This can be explained by the ultra-sensitive of non-collinear conical magnetic structure and spin-phonon coupling in BFSO to the DLD related local lattice structure. The above findings enable better understanding and usage of lattice defects on regulating the physical properties of multiferroic hexaferrite devices.

Electronic and magnetic properties of iridium ilmenites AIrO3 (A=Mg, Zn, and Mn)

We theoretically investigate the electronic band structures and magnetic properties of ilmenites with edge-sharing IrO$_6$ honeycomb layers, $A$IrO$_3$ with $A=$ Mg, Zn, and Mn, in comparison with a collinear antiferromagnet MnTiO$_3$. The compounds with $A=$ Mg and Zn were recently reported in Y.~Haraguchi {\it et al.}, Phys. Rev. Materials {\bf 2}, 054411 (2018), while MnIrO$_3$ has not been synthesized yet but the honeycomb stacking structure was elaborated in a superlattice with MnTiO$_3$ in K.~Miura {\it et al.}, Commun. Mater. {\bf 1}, 55 (2020). We find that, in contrast to MnTiO$_3$, where an energy gap opens in the Ti $3d$ bands by antiferromagnetic ordering of the high-spin $S=5/2$ moments, MgIrO$_3$ and ZnIrO$_3$ have a gap in the Ir $5d$ bands under the influence of both spin-orbit coupling and electron correlation. Their electronic structures are similar to those in the spin-orbit coupled Mott insulators with the $j_{\rm eff}=1/2$ pseudospin degree of freedom, as found in monoclinic $A_2$IrO$_3$ with $A=$ Na and Li which have been studied as candidates for the Kitaev spin liquid. Indeed, we find that the effective exchange interactions between the $j_{\rm eff}=1/2$ pseudospins are dominated by the Kitaev-type bond-dependent interaction and the symmetric off-diagonal interactions. On the other hand, for MnIrO$_3$, we show that the local lattice structure is largely deformed, and both Mn $3d$ and Ir $5d$ bands appear near the Fermi level in a complicated manner, which makes the electronic and magnetic properties qualitatively different from MgIrO$_3$ and ZnIrO$_3$. Our results indicate that the IrO$_6$ honeycomb network in the ilmenites $A$IrO$_3$ with $A=$ Mg and Zn would offer a good platform for exotic magnetism by the spin-orbital entangled moments like the Kitaev spin liquid.

Effective continuum model of twisted bilayer GeSe and origin of the emerging one-dimensional mode

The electric structure of twisted bilayer GeSe, which shows a rectangular moir\'{e} pattern, is analyzed using a $\bm{k}\cdot\bm{p}$ type effective continuum model. The effective model is constructed on the basis of the the local approximation method, where the local lattice structure of a twisted bilayer system is approximated by its untwisted bilayer with parallel displacement, and the required parameters are fixed with the help of the first-principles method. By inspecting the twist angle dependence of the physical properties, we reveal a relation between the effective potential under moir\'{e} pattern and the alignment of the Ge atoms, and also the resultant one-dimensional flat band, where the band is flattened stronger in a specific direction than the perpendicular direction. Due to the relatively large effective mass of the original monolayers, the flat band with its band width as small as a few meV appear in a relatively large angle. This gives us an opportunity to explore the dimensional crossover in the twisted bilayer platform.

Super-resolved Optical Mapping of Reactive Sulfur-Vacancies in Two-Dimensional Transition Metal Dichalcogenides.

Transition metal dichalcogenides (TMDs) represent a class of semiconducting two-dimensional (2D) materials with exciting properties. In particular, defects in 2D-TMDs and their molecular interactions with the environment can crucially affect their physical and chemical properties. However, mapping the spatial distribution and chemical reactivity of defects in liquid remains a challenge. Here, we demonstrate large area mapping of reactive sulfur-deficient defects in 2D-TMDs in aqueous solutions by coupling single-molecule localization microscopy with fluorescence labeling using thiol chemistry. Our method, reminiscent of PAINT strategies, relies on the specific binding of fluorescent probes hosting a thiol group to sulfur vacancies, allowing localization of the defects with an uncertainty down to 15 nm. Tuning the distance between the fluorophore and the docking thiol site allows us to control Föster resonance energy transfer (FRET) process and reveal grain boundaries and line defects due to the local irregular lattice structure. We further characterize the binding kinetics over a large range of pH conditions, evidencing the reversible adsorption of the thiol probes to the defects with a subsequent transitioning to irreversible binding in basic conditions. Our methodology provides a simple and fast alternative for large-scale mapping of nonradiative defects in 2D materials and can be used for in situ and spatially resolved monitoring of the interaction between chemical agents and defects in 2D materials that has general implications for defect engineering in aqueous condition.

Polycomponent doping improved thermoelectric performance of Cu<sub>3</sub>SbSe<sub>4</sub>-based solid solutions

<sec> Cu<sub>3</sub>SbSe<sub>4</sub>, one of the ternary p-type semiconductor materials with chalcopyrite structure, has aroused much interest in thermoelectrics due to its inherent large effective mass and narrow bandgap. Therefore, many researches have been done, which cover the single and/or multi-element doping to manipulate its band structure and introduce the point defects. Although great achievements have been made in recent years, the mechanism in Cu<sub>3</sub>SbSe<sub>4</sub> with respect to the phonon and electronic transport properties needs further investigating. </sec><sec> In this work, first, Sn and S are co-doped into Cu<sub>3</sub>SbSe<sub>4</sub> and then the resulting compound is alloyed with Ga<sub>2</sub>Te<sub>3</sub>, to improve its TE performance and understand the mechanism by calculating the band structure and crystal structure. The calculation of band structure reveals that an impurity band is created within the bandgap after co-doping Sn and S due to their contributions to the density of the states (DOS), which is directly responsible for the significant improvement in carrier concentration (<i>n</i><sub>H</sub>) and electrical property. Therefore, the power factor (PF) is enhanced from 0.52 × 10<sup>–3</sup> to 1.3 × 10<sup>–3</sup> W·m<sup>–1</sup>·K<sup>–2</sup>. </sec><sec> Although the effect associated with the Ga (Te) residing at Sb (Se) sites on the band structure is limited due to the fact that both the single Ga- and single Te-doped band structure remain almost unchanged, the structural parameters (bond lengths and angles) of the polyhedrons [SeCu<sub>3</sub>Sb] and [SbSe<sub>4</sub>] before and after Te and Ga residing at Se and Sb sites respectively change remarkably. This yields the significant distortion of local lattice structure on an atomic scale. Therefore, the phonon scattering is enhanced and the lattice thermal conductivity (<i>κ</i><sub>L</sub>) decreases from 1.23 to 0.81 W·K<sup>–1</sup>·m<sup>–1</sup> at 691 K. The reduction in <i>κ</i><sub>L</sub> prevents the total thermal conductivity (<i>κ</i>) from being enhanced rapidly. As a consequence, the highest ZT value of 0.64 is attained, which is much higher than that of the pristine Cu<sub>3</sub>SbSe<sub>4</sub> (ZT = 0.26). In addition, we not only present a synergistic strategy to separately optimize the phonon and electronic properties, but also fully elaborate its mechanism and better understand that this strategy is an effective way to improve the TE performance of the Cu<sub>3</sub>SbSe<sub>4</sub>-based solid solutions.</sec>