Density Of Vacancies Research Articles

Conductometric sensor for gaseous sulfur-mustard simulant by gold nanoparticles anchored on ZnO nanosheets prepared via microwave irradiation

We report the microwave-assisted synthesis of Au nanoparticles (NPs) anchored porous ZnO nanosheets (Au-ZnO NSs) and their application in the sensitive detection of 2-chloroethyl ethyl sulfide (2-CEES) vapors, which are a simulant of sulfur mustard chemical weapon. Upon microwave irradiation for < 1 min with an annealing, highly crystalline Au NPs with a narrow particle-size distribution (2.32 ± 0.40 nm) are densely formed on the surface of porous ZnO NSs, which increases the density of oxygen vacancies in the ZnO. Under the optimal working temperature (450 °C), the response of the Au-ZnO NS sensor was measured to be 787 for 10 ppm 2-CEES, which is ∼14 times higher than that observed for the bare porous ZnO NSs-based sensor. Moreover, Au-ZnO NSs can detect 2-CEES gas even under high humidity (∼80 %) benefiting from its high sensitivity. The highly reproducible sensing performance was verified by repeated sensing test (20 times for 12 h). According to gas screening data, the Au-ZnO NSs exhibited outstanding selectivity toward sulfide compounds due to the high Au-S affinity. In summary, we have successfully demonstrated a simple and facile approach to form the Au-ZnO heterostructure by microwave irradiation and enhanced the gas-sensing performance by inducing catalytic activity.

Electrospun TiO2 Nanofibers Featuring Surface Oxygen Vacancies as a Multifunctional Interlayer for High-Performance Lithium-Sulfur Batteries in a Wide Temperature Range.

Despite great achievements having been made in lithium-sulfur batteries (LSBs), further improvements regarding rate performance, cycle life, and operating temperature are needed for realistic applications. Herein, we developed a simple electrospun method for the preparation of TiO2 coaxial nanofiber (TCNFs)-modified Celgard separators to suppress the polysulfide shuttling. LSBs with a TCNF/Celgard separator display excellent electrochemical performance. For an areal sulfur loading of 2.5 mg cm-2, the cells exhibited a capacity of 1279 mA h g-1 at 0.5 A g-1, remained 798 mA h g-1 at 2.5 A g-1, and low-capacity decay of 0.057% per cycle within 1000 cycles. At 50 and -10 °C, the capacity of the cells is maintained at 932 and 931 mA h g-1 after 80 cycles at 0.5 A g-1, respectively. Detailed structural analysis and theoretical calculations revealed that the hollow-structured TCNFs offer high density of accessible electropositive Ti sites and oxygen vacancies and thus enables efficient trapping of polysulfides and facilitates Li+ transfer, leading to excellent performance. The simplicity of this strategy and the diversity of hollow-structured metal oxides holds great promise to design separators for high-performance LSBs.

Characterization of the Response of Magnetron Sputtered In2O3-x Sensors to NO2.

The response of resistive In2O3-x sensing devices was investigated as a function of the NO2 concentration in different operative conditions. Sensing layers are 150 nm thick films manufactured by oxygen-free room temperature magnetron sputtering deposition. This technique allows for a facile and fast manufacturing process, at same time providing advantages in terms of gas sensing performances. The oxygen deficiency during growth provides high densities of oxygen vacancies, both on the surface, where they are favoring NO2 absorption reactions, and in the bulk, where they act as donors. This n-type doping allows for conveniently lowering the thin film resistivity, thus avoiding the sophisticated electronic readout required in the case of very high resistance sensing layers. The semiconductor layer was characterized in terms of morphology, composition and electronic properties. The sensor baseline resistance is in the order of kilohms and exhibits remarkable performances with respect to gas sensitivity. The sensor response to NO2 was studied experimentally both in oxygen-rich and oxygen-free atmospheres for different NO2 concentrations and working temperatures. Experimental tests revealed a response of 32%/ppm at 10 ppm NO2 and response times of approximately 2 min at an optimal working temperature of 200 °C. The obtained performance is in line with the requirements of a realistic application scenario, such as in plant condition monitoring.

Luminescent iron disilicide film growth by metal–organic chemical vapor deposition

Semiconducting iron disilicide (β-FeSi2) films were epitaxially grown on the Ag-layer pre-coated Si(111) substrates with an initial β-FeSi2 layer by the metal–organic chemical vapor deposition method. These β-FeSi2 films had (101)-preferred orientations, and their crystal quality was improved as the growth temperature increased from 893 to 1093 K. The photoluminescence (PL) intensity of the (101)-oriented β-FeSi2 films grown at 973 K was larger than those of β-FeSi2 films at the other deposition temperatures, which indicates the decrease of the density of nonradiative recombination centers in β-FeSi2. A clear A-band emission originated from β-FeSi2 was observed for these films up to 285 K. This pronounced PL intensity enhancement from β-FeSi2 is attributed not only to the crystallinity evaluated by XRD measurement but also to the decrease in density of thermal equilibrium Si vacancy in β-FeSi2.

Chiral zero-energy modes in the disordered α−T3 lattice

The $\ensuremath{\alpha}\text{\ensuremath{-}}{T}_{3}$ lattice is an interpolate between the graphene $(\ensuremath{\alpha}=0)$ and the Dice lattices $(\ensuremath{\alpha}=1)$ and has a nondispersive flat band across the Dirac bands at the band center $(E=0)$. In this paper, we study the delocalization effect of the additional chiral zero-energy modes (CZEM) from the vacancy disorder in the $\ensuremath{\alpha}\text{\ensuremath{-}}{T}_{3}$ lattice and address the influence of the flat band on the CZEM. It is shown that the mere broadening of the flat band without the CZEM could produce a supermetallic phase around the band center $E\ensuremath{\sim}0$ as well as an adjoined narrow localization regime. When the CZEM from the vacancy disorder is turned on, the transport property resembles the graphene case $(\ensuremath{\alpha}=0)$ that electrons in the low-energy regime are fully localized except the Dirac point of $E=0$, which is a critical delocalization point because the zero-energy conductivity (ZEC) is independent of the inelastic-scattering strength $\ensuremath{\eta}$. But the ZEC itself is shown to weakly rely on both the model parameter $\ensuremath{\alpha}$ and the vacancy density ${n}_{c}$ due to the broadening effect of the flat band. The extreme vacancy imbalance among each ABC site of a primitive cell is also studied, and the electron transport around $E\ensuremath{\sim}0$ is changed to be either the pure inelastic disorder case without vacancy or the fully localized phase without the critical delocalization point of $E=0$, which depends on the central site $B$ atom replaced by vacancy or not.

Effect of Oxygen Vacancy on the Crystallinity and Optical Band Gap in Tin Oxide Thin Film

Herein, we have prepared tin oxide (SnO2) nanoparticles (NPs), through a co-precipitation method, using SnCl2·2H2O dissolved in distilled water (DW) as a precursor. Then, the prepared NPs were heat treated in a muffle furnace, as a function of temperature, under an open atmosphere. The prepared SnO2 NPs were then re-dispersed in DW, followed by spray casting on a glass substrate, for preparing SnO2 thin films. The average thickness of the fabricated SnO2 thin films was 2.76 µm. We demonstrated a very clear variation in the structural, compositional, and morphological features of the different films (in particular, variation of the density of oxygen vacancies), which altered their electrical and optical properties. Raising the calcination temperature of the SnO2 thin films, from 250 °C to 650 °C, led to a monotonic reduction in the crystallite size, from 10.4 nm to 6.7 nm, and a decrease in the O/Sn ratio, from 5.60 to 4.79. A 14.5% decrease in the O/Sn ratio resulted in a decrease in the crystallite size by 3.7 nm (i.e., a 35.3% decrease in the NP size), and a decrease in the band gap of 0.11 eV. The lowering of the band gap, along with an increase in the oxygen vacancies in the films, accords well with previous studies. Besides, as the calcination temperature was raised, the refractive index and absorption coefficient values were also found to notably increase. Very interestingly, by simply altering the calcination temperature, we were able to produce SnO2 thin films with optical band gaps nearly equal to the fundamental band gap (2.96 eV), even though many earlier experimental studies had reported considerably greater values (3.36–4.24 eV). SnO2 thin films with lower oxygen vacancies exhibited relatively higher band gaps, which is likely to be favorable for the desired electron transport layer in perovskite solar cells.

Self-supported iridium-ruthenium oxides catalysts with enriched phase interfaces for boosting oxygen evolution reaction in acid

Developing highly efficient low-noble-metal loading electrocatalysts for acidic oxygen evolution reaction (OER) remains a great challenge. Herein, we developed a novel self-supported IrmRunOx/Ti electrode exhibiting an amorphous film encapsulated with a small number of crystalline nanoparticles for efficient acidic OER. The as-synthesized Ir0.95Ru0.05Ox/Ti electrode exhibits an excellent OER performance with an overpotential of 200 mV at 10 mA cm−2, a Tafel slope of 46.8 mV dec-1, and robust stability of 192 h in 0.1 M HClO4. The enriched heterogeneous interfaces between the amorphous phase and crystalline phase enhance the stability and activity of the solid solution oxides. The high density of oxygen vacancies on the surface, together with the strong electronic interaction contribute to boosting the OER. This work provides some valuable insights into developing efficient Ir-based catalysts for acidic water splitting.

Giant dielectric properties of Na1/2La1/2Cu3Ti4O12 perovskite ceramic: First-principles and experimental investigations

Na1/2La1/2Cu3Ti4O12 ceramics were successfully fabricated via a sol-gel method. We found that the crystal structure of these sintered ceramics is identical to that of CaCu3Ti4O12, ICSD number 01-075-2188. A small quantity of CuO was observed due to the substitution of Na + at Cu2+ sites of the CaCu3Ti4O12 structure. Additionally, a small number of related Cu phases were discovered at grain junctions in these ceramics. Our Ab initio Molecular Dynamic simulations clearly revealed that oxygen vacancies are created during the sintering process. Additionally, at room temperature, our simulations showed that sites of the oxygen vacancies in the Na1/2La1/2Cu3Ti4O12 lattice are occupied by free oxygen, resulting in a lower oxygen vacancy density. Sintered Na1/2La1/2Cu3Ti4O12 ceramics present excellent dielectric properties, a high dielectric permittivity of 7780–9000 and a rather low dielectric loss tangent (0.041–0.042). From our electron density analysis, it was clearly seen that Cu+ and Ti3+ observed by the XPS measurements originated from the presence of oxygen vacancies in the Na1/2La1/2Cu3Ti4O12 structure. Electrical, DFT, and XPS studies indicated that the internal barrier layer capacitor (IBLC) model is the most appropriate for the colossal dielectric response in these ceramics.

Effect of the TiO2 electron transport layer thickness on charge transfer processes in perovskite solar cells

Dense TiO2 thin films are widely used as electron transport layers in perovskite solar cells. TiO2 is a high band gap semiconductor with n-type conductivity showing excellent compatibility with metal-halide perovskites in terms of energy alignment providing efficient charge separation and less energy loss of electrons during electron transfer. In this work, TiO2 layers were deposited from TiO2 sol-gel solution by spin-coating methods. The optimization of TiO2 ETL thickness is a necessary procedure to reduce ETL resistance and minimize charge recombination. The thickness reduction leads to a decrease in resistance, however, also enhances charge recombination due to the formation of pin-holes and cracks. We found that TiO2 thickness reduction also causes the TiO2 defects density changes. By studying luminescence spectra of TiO2 with various thicknesses we found that the thickness reduction leads to the increase in the interstitial Ti+3 defects density, while the oxygen vacancies density decreases. Ti+3 species form deep levels trapping free electrons and as result increasing TiO2 resistance. TiO2 films with thicknesses in the range of 40–120 nm were deposited and used as ETL for PSCs with ITO/TiO2/CH3NH3I3PbClx/CuPc/MoOx/Ag structure. Our study revealed two competitive charge transport processes taking place in TiO2: electron transport through the TiO2 conduction band and electron trapping by deep trap levels formed by Ti+3 species. Therefore according to the IV and IS studies, the optimal TiO2 layer thickness at which there is a balance between the competitive charge transport processes is about 60 nm for our deposition condition.

Ligand vacancy channels in pillared inorganic-organic hybrids for electrocatalytic organic oxidation with enzyme-like activities

Simultaneously achieving abundant and well-defined active sites with high selectivity has been one of the ultimate goals for heterogeneous catalysis. Herein, we construct a class of Ni hydroxychloride-based inorganic-organic hybrid electrocatalysts with the inorganic Ni hydroxychloride chains pillared by the bidentate N-N ligands. The precise evacuation of N-N ligands under ultrahigh-vacuum forms ligand vacancies while partially retaining some ligands as structural pillars. The high density of ligand vacancies forms the active vacancy channel with abundant and highly-accessible undercoordinated Ni sites, exhibiting 5-25 fold and 20-400 fold activity enhancement compared to the hybrid pre-catalyst and standard β-Ni(OH)2 for the electrochemical oxidation of 25 different organic substrates, respectively. The tunable N-N ligand can also tailor the sizes of the vacancy channels to significantly impact the substrate configuration leading to unprecedented substrate-dependent reactivities on hydroxide/oxide catalysts. This approach bridges heterogenous and homogeneous catalysis for creating efficient and functional catalysis with enzyme-like properties.

Appropriate oxygen vacancies and Mo-N bond synergistically modulate charge transfer dynamics of MoO3-x/S-CN for superior photocatalytic disinfection: Unveiling synergistic effects and disinfection mechanism.

Highly efficient charge transfer is a critical factor to modulate the photocatalytic activity. However, the conscious modulation of charge transfer efficiency is still a great challenge. Herein, a novel interfacial Mo-N bond and appropriate oxygen vacancies (OVs) modulated S-scheme MoO3-x/S-CN heterojunction was rationally fabricated for efficient photocatalytic disinfection. The results of characterizations and density functional theory (DFT) calculations suggested that the enhanced charge transfer dynamics is ascribed to the optimizing oxygen vacancies density and forming interfacial Mo-N bond. It can improve charge transfer efficiency from 36.4% (MoO3-x) to 52.5% (MoO3-x/S-CN) and produce more reactive oxygen species (ROS), achieving entirely inactivate of 7.60-log E. coli and S. aureus within 50min and 75min. Besides, MoO3-x/S-CN can well resist the disturbance from the coexisting substances, and can be applied in a wide pH range, and even authentic water bodies. Monitoring of bacterial antioxidant systems and membrane integrity revealed that bacterial inactivation begins with the oxidation of cell membrane and dies from leakage of intracellular substances and destruction of cell structure. This work provides an inspiration on consciously modulating S-scheme charge transfer efficiency by optimizing oxygen vacancies density and atomic-level interface control for promoting the photocatalytic antibacterial activity.

Performance improvement of a tunnel junction memristor with amorphous insulator film

This study theoretically demonstrated the oxygen vacancy (VO2+)-based modulation of a tunneling junction memristor (TJM) with a high and tunable tunneling electroresistance (TER) ratio. The tunneling barrier height and width are modulated by the VO2+-related dipoles, and the ON and OFF-state of the device are achieved by the accumulation of VO2+ and negative charges near the semiconductor electrode, respectively. Furthemore, the TER ratio of TJMs can be tuned by varying the density of the ion dipoles (Ndipole), thicknesses of ferroelectric-like film (TFE) and SiO2 (Tox), doping concentration (Nd) of the semiconductor electrode, and the workfunction of the top electrode (TE). An optimized TER ratio can be achieved with high oxygen vacancy density, relatively thick TFE, thin Tox, small Nd, and moderate TE workfunction.

Epitaxial Grown VO2 with Suppressed Hysteresis and Low Room Temperature Resistivity for High-Performance Thermal Sensor Applications

The ability of VO2 to undergo semiconductor-to-metal phase transition (SMT) upon heating makes it a very attractive material for uncooled bolometers. The SMT of VO2 represents a large temperature coefficient of resistance, which is an important parameter for the development of highly responsive microbolometers. However, other characteristics of the SMT of VO2 such as its high transition temperature (341.2 K), the sharpness of the transition, its hysteresis, and the high room temperature resistivity limit the performance of this material in microbolometers. In this work, we grow a high-quality epitaxial ultrathin film VO2 on c-plane Al2O3 by pulsed laser deposition. The low deposition temperature and tuning the oxygen partial pressure during the growth process enable control over the grain size and oxygen vacancy concentration. This allowed controlling the SMT parameters of the samples. In particular, we show that the high density of grain boundaries associated with nanosized grains suppresses the thermal hysteresis of the SMT. Simultaneous control over the density of oxygen vacancies and the size of grains enables the adjustment of the temperature coefficient of resistance, room temperature resistivity, SMT temperature, sharpness, and thermal hysteresis toward suitable values for the fabrication of efficient VO2-based uncooled bolometers. Compared with other VO2 fabrication methods, this approach can be viewed as a simpler alternative for VO2 fabrication with favorable properties for practical bolometer applications.

Metastable pitting corrosion behavior and characteristics of passive film of laser powder bed fusion produced Ti–6Al–4V in NaCl solutions with different concentrations

This work investigated the metastable pitting corrosion mechanism of laser powder bed fusion (LPBF) produced Ti–6Al–4V. The passive films of samples were produced by potentiostatic polarization in NaCl solutions with different concentrations, and electrochemical measurements were employed to understand the influence of Cl- on the characteristics of passive films. The frequency of pitting nucleation and the pit dimension increase with increased Cl- concentration. The attack of Cl- promotes the dissolution of passive films. A higher density of oxygen vacancies is produced in passive film because of the ingressive Cl-, resulting in the condensation of voids and pitting corrosion.

High-temperature operation of gallium oxide memristors up to 600 K

Memristors have attracted much attention for application in neuromorphic devices and brain-inspired computing hardware. Their performance at high temperatures is required to be sufficiently reliable in neuromorphic computing, potential application to power electronics, and the aerospace industry. This work focuses on reduced gallium oxide (GaOx) as a wide bandgap memristive material that is reported to exhibit highly reliable resistive switching operation. We prepared amorphous GaOx films to fabricate Pt/GaOx/indium tin oxide memristors using pulsed laser deposition. Stable resistive switching phenomena were observed in current–voltage properties measured between 300 and 600 K. The conduction mechanism analysis revealed that the resistive switching is caused by the transition between ohmic and space charge limiting current conductions. We elucidated the importance of appropriate control of the density of oxygen vacancies to obtain a high on/off resistance ratio and distinct resistive switching at high temperatures. These results indicate that GaOx is a promising memristor material that can be stably operated even at the record-high temperature of 600 K.

Impact of the Ultrasonic-Assisted Casting of an AlSi7Mg Alloy on T6 Heat Treatment

In this work, the effect of ultrasonic vibration during solidification on the aging kinetics of an AlSi7Mg alloy is investigated. With the ultrasonic equipment coupled to the mold walls, melt treatment was performed by two approaches: (i) fully above liquidus (&gt;635 °C); and (ii) in the full range between liquidus and solidus (630 °C→ 550 °C). Cast samples were then subjected to T6 heat treatment for different aging times. It is shown that indirect ultrasound treatment increases the cooling rate while active. The eutectic Si was refined and further modified when ultrasound treatment was performed in the semisolid state. Due to the significant release of solute during the decomposition of π-Al8FeMg3Si6 into fine β-Al5FeSi, this has a significant impact in the solution stage. Ultrasound treatment fully above liquidus decreased the underaging time to 50% and peak aging time to 25% without compromising strength. The results suggest aging kinetics are correlated with a higher vacancy density and solute enrichment which favors Guinier–Preston (GP) zone formation. These findings show a promising route to tailor the aging kinetics in these alloys by selectively modifying phases and cooling rates.

Nanodiamonds Doped with Manganese for Applications in Magnetic Resonance Imaging.

Nanodiamonds (NDs) are emerging with great potential in biomedical applications like biomarking through fluorescence and magnetic resonance imaging (MRI), targeted drug delivery, and cancer therapy. The magnetic and optical properties of NDs could be tuned by selective doping. Therefore, we report multifunctional manganese-incorporated NDs (Mn-NDs) fabricated by Mn ion implantation. The fluorescent properties of Mn-NDs were tuned by inducing the defects by ion implantation and enhancing the residual nitrogen vacancy density achieved by a two-step annealing process. The cytotoxicity of Mn-NDs was investigated using NCTC clone 929 cells, and the results revealed no cytotoxicity effect. Mn-NDs have demonstrated dual mode contrast enhancement for both T 1- and T 2-weighted in vitro MR imaging. Furthermore, Mn-NDs have illustrated a significant increase in longitudinal relaxivity (fivefold) and transversal relaxivity (17-fold) compared to the as-received NDs. Mn-NDs are employed to investigate their ability for in vivo MR imaging by intraperitoneal (ip) injection of Mn-NDs into mice with liver tumors. After 2.5 h of ip injection, the enhancement of contrast in T 1- and T 2-weighted images has been observed via the accumulation of Mn-NDs in liver tumors of mice. Therefore, Mn-NDs have great potential for in vivo imaging by MR imaging in cancer therapy.

A confinement strategy for constructing CexMn1−xO2 solid solutions with oxygen vacancies confined in interwoven titania nanotubes toward catalytic ozonation of 1,2-dichloroethane

Catalytic ozonation is an effective method to control chlorinated volatile organic compounds (CVOCs) emissions in industrial plants. Here, a series of CexMn1−xO2 mixed oxides with different atomic ratios confined on tubular titanium nanotubes (TNTs) were prepared and evaluated for catalytic ozonation of CVOCs, employing 1,2-dichloroethane (DCE) as the model molecule. For dual-site CexMn1−xO2/TNTs catalysts, Ce doping on MnO2/TNTs triggered the formation of surface lattice defects, resulting in an increase in the density of oxygen vacancies but a decrease in strong-acidity sites. The Ce0.3Mn0.7O2/TNTs catalyst obtained DCE removal efficiency of 96.7% with CO2 selectivity of 86.0% during 18 h, and performed good reproducibility of 4 cycles and moderate water vapor resistance at room temperature. The catalytic activity of CexMn1−xO2/TNTs catalysts was influenced significantly by the acidity content and the oxygen vacancies concentration. Based on six types of by-products and Fukui index analysis, three conceivable reaction pathways of DCE decomposition were proposed. This work deepens the understanding of dual-site catalysts to catalytic ozonation of CVOCs and develops a new platform for hazardous-air treatment.

Elucidating the crystal-facet dependent catalytic performance of coupled flake-CuO/Cu-zeolite hybrid catalysts for coal-gas-SCR

Multi-active sites were usually molded to achieve better catalytic performance for those reactions involving multiple reactants. In this work, CuO/Cu-ZSM-5 (CuO/Cu-Z5) hybrid catalysts with structurally well-defined CuO nanoparticles and site-isolated Cu ions were synthesized and applied for selective catalytic reduction by coal-gas (coal-gas-SCR). The activity evaluation reveals that participation of CuO could significantly improve NOx conversion of Cu-Z5, and Flake-CuO nanoparticle exhibits the best catalytic performance. Several comprehensive characterizations manifest that Flake-CuO/Cu-Z5 contains the highest density of oxygen vacancies, on which the richly exposed CuO (200) facet shows high oxygen mobility and low oxygen vacancy formation energy that verified by DFT calculation. Additionally, Flake-CuO provides superior redox ability and highly active sites for NO adsorption and oxidation to NO2, which can remarkably accelerate subsequent SCR rates. In situ DRIFTS demonstrates that more adsorbed NO2 and bidentate nitrate species generated on Flake-CuO/Cu-Z5, and the amount of other vital intermediate species (such as NHx and CH3NO) were also largely formed over the sample. Interestingly, after injecting reductants, the bidentate nitrate on Rod-CuO/Cu-Z5, Sheet-CuO/Cu-Z5, and Cu-Z5 is partially transformed to monodentate nitrate, whereas Flake-CuO/Cu-Z5 could prohibit this process due to those substantial chemisorbed oxygen and appropriate adsorption ability of intermediates species over CuO (200) facet. The mass migration between CuO and Cu2+ ions revealed that CuO (200) facet not only catalyzes the SCR reaction but also could transfer those formed nitrates and activated reactants to Cu2+ ions in zeolite framework nearby to accomplish the following reaction, fulfilling the acceleration of SCR process.

Evolution of austenite lattice parameter during isothermal transformation in a 0.4 C low alloyed steel

The evolution of internal stress during displacive transformation is a topic of continuous debate. Neutron diffraction was used to study the isothermal bainite transformation in a 0.4 C low alloyed steel from 773 to 623 K to provide a clearer basis for discussion regarding the change in the austenite lattice parameter. According to diffraction profile analysis, fresh bainite possesses a body-centered tetragonal structure, and its c/a ratio decreases rapidly over time. The austenite lattice parameter increases or decreases depending on whether the transformation temperature is above or below the nose of the Time-Temperature-Transformation (TTT) curve. This isothermal transformation behavior can be divided into two categories: above and below the nose of TTT curve, which correspond to the upper and lower bainites, respectively. The internal stresses caused by the transformation strains are relaxed by dislocation motion and vacancy formation. The yielded dislocations and vacancies not only affect the broadening of both austenite and bainitic ferrite diffraction peaks but also the lattice parameter. The first-principles calculations demonstrate that the austenite lattice parameter decreases as the vacancy density increases, which may account for the experimental observation in lower bainite.