Zhen Li

Beihang University | BUAA · School of Material Science and Engineering

Thermal conductivity (κ) is one of the fundamental properties of materials for phase change memory (PCM) application, as the set/reset processes strongly depend upon heat dissipation and transport. The κ of phase change materials in both amorphous and crystalline phases should be quite small, because it determines how energy-efficient the PCM devic...

Antimony telluride (Sb2Te3) has a very low ZT value at room temperature, even though the alloys of Bi2Te3 and Sb2Te3 are the most widely used thermoelectric materials. Taking advantage of nano-structures and topological insulators (TIs), we report that high ZT values of larger than 2 can be achieved in one quintuple-layer (QL, ZT ≥ 2.1) and 4 QLs (...

We present a first-principles framework to extract deformation potentials in silicon based on density-functional theory (DFT) and density-functional perturbation theory (DFPT). We compute the electronic band structures, phonon dispersion relations, and electron-phonon matrix elements to extract deformation potentials for acoustic and optical phonon...

We present an efficient method for accurately computing electronic scattering rates and transport properties in materials with complex band structures. Using ab initio simulations, we calculate a limited number of electron–phonon matrix elements, and extract scattering rates for acoustic and optical processes based on deformation potential theory....

Inspired by the remarkable performance of SnSe‐based compounds in thermoelectrics, a strontium‐tin‐selenium (SrSnSe2) compound is theoretically designed, observing anisotropic Rashba spin‐orbital splitting and strong four‐phonon scattering behavior. Through comprehensive analyses of elastic constants, phonon dispersion, and ab initio molecular dyna...

Over the last two decades a plethora of new thermoelectric materials, their alloys, and their nanostructures were synthesized. The ZT figure of merit, which quantifies the thermoelectric efficiency of these materials increased from values of unity to values consistently beyond two across material families. At the same time, the ability to identify...

Over the last two decades a plethora of new thermoelectric materials, their alloys, and their nanostructures were synfthesized. The ZT figure of merit, which quantifies the thermoelectric efficiency of these materials increased from values of unity to values consistently beyond two across material families. At the same time, the ability to identify...

The design of highly efficient and stable electrocatalysts in hydrogen evolution reaction over a wide range of pH, especially in neutral or alkaline conditions, is of great significance but remains· challenging. Herein, a family of single‐atoms and clusters inside the N‐doped porous carbon matrix (NDPCM) are encapsulated. Specifically, the single‐a...

The increasing energy demand and the ever more pressing need for clean technologies of energy conversion pose one of the most urgent and complicated issues of our age. Thermoelectricity, namely the direct conversion of waste heat into electricity, is a promising technique based on a long-standing physical phenomenon, which still has not fully de...

Mobility is a key parameter for SnO2, which is extensively studied as a practical transparent oxide n-type semiconductor. In experiments, the mobility of electrons in bulk SnO2 single crystals varies from 70 to 260 cm2V−1s−1 at room temperature. Here, we calculate the mobility as limited by electron–phonon and ionized impurity scattering by couplin...

Mobility is a key parameter for SnO2, which is extensively studied as a practical transparent oxide n-type semiconductor. In experiments, the mobility of electrons in bulk SnO2 single crystals varies from 70 to 260 cm2V-1s-1 at room temperature. Here, we calculate the mobility as limited by electron-phonon and ionized impurity scattering by couplin...

This paper introduces ElecTra, an open-source code which solves the linearized Boltzmann transport equation in the relaxation time approximation for charge carriers in a full-band electronic structure of arbitrary complexity, including their energy, momentum, and band-index dependence. ElecTra stands for 'ELECtronic TRAnsport' and computes the elec...

Low bandgap thermoelectric materials suffer from bipolar effects at high temperatures, with increased electronic thermal conductivity and reduced Seebeck coefficient, leading to reduced power factor and low ZT figure of merit. In this work we show that the presence of strong transport asymmetries between the conduction and valence bands can allow h...

Low band gap thermoelectric materials suffer from bipolar effects at high temperatures, with increased electronic thermal conductivity and reduced Seebeck coefficient, leading to reduced power factor and low ZT figure of merit. In this work we show that the presence of strong transport asymmetries between the conduction and valence bands can allow...

A CeO2-dispersed nickel-aluminide coating was deposited by aluminizing a Ni-CeO2 electroplating film with a Ni-Re interlayer pre-electroplated sequentially. The CeO2-dispersed coating was exposed to dry and wet CO2 gas at 650 °C for 1300 h. Internal oxidation and cavities were observed in the coating centralized around CeO2 particles, which became...

The aluminide coatings with and without Si modification were prepared on the new γ′-strengthened cobalt-based superalloy using a pack cementation method. Cyclic oxidation of the coated Co-based superalloy was study at 1050 °C. The weight changes of Al coating and Al-Si coating were -4.28 mg/cm² after 248 cycles and -3.40 mg/cm² after 346 cycles, re...

The field of thermoelectric materials has undergone a revolutionary transformation over the last couple of decades as a result of the ability to nanostructure and synthesize myriads of materials and their alloys. The ZT figure of merit, which quantifies the performance of a thermoelectric material has more than doubled after decades of inactivity,...

The disadvantages of high power consumption and slow operating speed hinder the application of phase-change materials (PCMs) for a universal memory. In this work, based on a rigorous experimental scheme, we synthesized a series of YxSb2-xTe3 (0 ≤ x ≤ 0.333) PCMs and demonstrated that Y0.25Sb1.75Te3 (YST) is an excellent candidate material for the u...

Binary Sb2Te is considered as a potential recording material for phase-change memory due to its higher crystallization speed than the widely investigated ternary Ge-Sb-Te alloys. To further improve the performance of Sb2Te, various dopants such as scandium (Sc) have been explored. Yet, the thermal conductivity of the pristine and doped Sb2Te is unk...

Bismuth antimony telluride (BST) is the state-of-the-art utilized thermoelectric alloy near room temperature. The BST single quintuple layers (QLs) are expected to accomplish two objectives simultaneously with both the increased power factor and the reduced thermal conductivity. In this work, the mechanical and transport properties of BST single QL...

2D magnetic semiconductors are intriguing for their great potential applications in spintronic nanodevices. Despite intensive research for decades, intrinsically 2D magnetic Janus semiconductors are scarce and their design guideline remains elusive. Herein we propose new 2D Janus Cr2O2XY (X=Cl, Y=Br/I) ferromagnets with asymmetric out-of-plane stru...

Doping is used to improve the overall performance of rhombohedral Sb₂Te₃ for the application in phase-change memory (PCM). However, it is difficult and laborious to obtain the optimal dopants using the time-consuming trial and error way. By high-throughput ab initio calculations with experiments, the present work identified Scandium, Yttrium and Me...

As the most promising materials for phase-change data storage, the pseudobinary mGeTe•nSb2Te3 (GST) chalcogenides have been widely investigated. Nevertheless, an in-depth understanding of the thermal-transport property of GST is still lacking, which is important to achieve overall good performance of the memory devices. Herein, by using first-princ...

Composition regulation of semiconductors can engineer the band structures and hence optimize their properties for better applications. Herein, we report the BixSb2-xTe3 (BST) single QL with high ZT values (~1.2 to ~1.5) at 300 K across a wide range of compositions 0 < x ≤ 1. The improved description of band structures by the unfold method reveals t...

Oxygen is widely used to tune the performance of chalcogenide phase-change materials in the usage of phase-Change random access memory (PCRAM) which is considered as the most promising next-generation non-volatile memory. However, the microscopic role of oxygen in the write-erase process, i.e., the reversible phase transition between crystalline an...

Oxygen is widely used to tune the performance of chalcogenide phase-change materials in the usage of phase-Change random access memory (PCRAM) which is considered as the most promising next-generation non-volatile memory. However, the microscopic role of oxygen in the write-erase process, i.e., the reversible phase transition between crystalline an...