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ErxTi0.1Zr0.9–xO2–1.5x (x = 0.04, 0.05, 0.06, 0.07, 0.08) ceramics were synthesized by a solid-state reaction method. The influence of the Er3+ addition on the phase composition, Vickers hardness, fracture toughness, and thermal conductivity of this ceramic material was investigated. The X-ray diffraction results reveal that the c-ZrO2 content increases from 1.85 vol% to 33.89 vol%, and the percentage of t-ZrO2 decreases from 98.15 vol% to 66.11 vol% with the increase in Er3+ from 4 mol% to 8 mol%. Moreover, the addition of Er3+ is beneficial for the volume expansion of the unit cell. At the same time, the incorporation of Er3+ weakens the coordination of oxygen ions around the metal cations, resulting in a corresponding decrease in the tetragonality of the t-ZrO2. The Vickers hardness and fracture toughness of the ErxTi0.1Zr0.9–xO2–1.5x ceramics show increasing and decreasing trends, respectively. The thermal conductivity has a significant decline due to point defects caused by the Er3+ doping. The 8ETZ ceramic exhibits the highest Vickers hardness (12.7 GPa), lowest fracture toughness (7.6 MPa/m1/2), and lowest average thermal conductivity (1.85 W/(m·K)) in the range of 200 to 1000 °C. All of the above properties are higher than those of the Y2O3-stabilized ZrO2 ceramic.

Annotation In connection with the possible use of laser technological equipment in space the impact of nanosecond UV laser on copper and its alloys was investigated. At the pre-threshold mode, in the absence of obvious traces of melting, at an energy density of E = 0.1–1.0 J/cm2, the metal in the irradiated zone swelled up and traces of plastic deformation were found. The uplift arised as a result of the formation of an excessive number of point defects. With an increase of the number of impacting pulses, accumulation of damage occurred, despite the fact that the surface completely cools down during the time between pulses. The height of the resulting uplift reached 1 μm, and sometimes even slightly more. Sliding and cracking along grain boundaries occurred, as well as crystallographic slipping. The discovered effect of the impact of laser pulse on the metal surface, associated with the occurrence of uplift and the presence of plastic deformation, is similar to the well-known acoustoplastic, electroplastic, and magnetoplastic effects. The discovered effect was called optoplastic. Exceeding the laser damage threshold (E ∼ 1.0 J/cm2) leads to melting and evaporation of the metal with the formation of a crater. This is oppositely directed process, which suppresses the manifestations of the optoplastic effect.

Lewis acid–base passivation is a significant technique to achieve structural stability of perovskite solar cells (PSCs) by overcoming the issues of wide grain boundaries, crystal defects, and the instability of PSCs. In this work, the combined effects of thiophene with phthalocyanine (Pc) as isomers (S2 and S3) on the photovoltaic performance of PSCs were studied for the first time. Through density functional theory calculations, we confirmed that the position of the S atom in the structure affects Lewis acid–base interactions with under-coordinated Pb2+ sites. The morphology of methylammonium lead iodide (MAPbI3) for passivated devices was improved and thin dense layers with compact surface and large grain size were observed, leading to improvement of the charge extraction ability and reduction of non-radiative recombination and the trap density. A highest power conversion efficiency of 18% was achieved for the Pc S3 passivated device, which was 6.69% more than that of the controlled device. Furthermore, the Pcs passivated devices demonstrated remarkable stability under high-moisture and high-temperature conditions.

A new family of ternary nano-laminated compounds, MAB phases, are studied as a promising class of neutron shielding materials for applications within fusion reactors. The shielding capacity against high-energy neutrons was evaluated, and the damage tolerance of MoAlB against Si+ irradiation was investigated over the temperature range of RT- 600 °C. The linear attenuation coefficients of these materials over wide neutron-energy ranges imply that Mo(W)AlB have a high neutron shielding capacity. MoAlB shows a strong resistance to crack formation and excellent tolerance to amorphization under higher temperatures. The detailed thermal dynamic behaviors (reaction barrier and migration barrier) associated with the defects in MoAlB were studied through DFT calculations. Also, the lattice parameter changes are related to the formation of various point defects and the defect evolution evidenced by Rietveld refinement of the GIXRD and DFT calculations. MoAlB is confirmed to be a great candidate as a neutron shielding material.

High lattice thermal conductivity of intrinsic GeTe limits the wide application of GeTe-based thermoelectrics. Recently, the optimization of GeTe-based thermoelectric materials has been focusing on reducing lattice thermal conductivity via strengthening phonon scattering. In this study, we systematically studied thermoelectric properties of Se-alloyed Ge0.95Bi0.05Te via theoretical calculations, structural characterizations, and performance evaluations. Our results indicate that Se-alloying can induce dense point defects with mass/strain-field fluctuations and correspondingly enhance point defect phonon scattering of the Ge0.95Bi0.05Te matrix. Se-alloying might also change chemical bonding strength to introduce resonant states in the base frequency of Ge0.95Bi0.05Te matrix, which can strengthen Umklapp phonon scattering. Finally, a decreased lattice thermal conductivity from ∼1.02 W m−1 K−1 to ∼0.65 W m−1 K−1 at 723 K is obtained in Ge0.95Bi0.05Te1-xSex pellets with increasing the Se content from 0 to 0.3. A peak figure of merit of ∼1.6 at 723 K is achieved in Ge0.95Bi0.05Te0.7Se0.3 pellet, which is ∼77% higher than that of pristine GeTe. This study extends the understanding on the thermoelectric performance of GeTe.

Microstructures of monolithic high purity SiC and SiC with sintering additives after neutron irradiation to a fluence of 2.0–2.5 × 1024 n/m2 (E > 0.1 MeV) at 333–363 K and after post-irradiation annealing up to 1673 K were observed using a transmission electron microscopy. Results showed that no black spot defects or dislocation loops in SiC grains were found after the neutron irradiation for all of the specimens owing to the moderate fluence at low irradiation temperature. Thus, it is confirmed that these specimens were swelled mostly by the formation of point defects. Black spots and small dislocation loops were discovered only after the annealing process in PureBeta-SiC and CVD-SiC, where the swelling almost diminished. Anomalous-shaped YAG grains were found in SiC ceramics containing sintering additives. These grains contained dense black spots defects and might lose crystallinity after the neutron irradiation, while these defects may annihilate by recrystallization during annealing up to 1673 K. Amorphous grain boundary phase was also presented in this ceramic, and a large part of it was crystallized through post-irradiation annealing and could affect their recovery behavior.

The specific luminescence behavior of crystalline oxide particles doped with rare earth ions strongly depends on the initial composition of the host material and synthesis conditions. This issue is especially significant for non-isovalent doping in the crystal lattice. In this case, the formation of the structure is accompanied by the formation of point defects serving as charge compensators. The work is devoted to the synthesis of CaWO4:Nd3+ particles in the salt melt (modified Pechini method) and the study of structural and luminescent properties under varying synthesis conditions. It was found that temperature and duration of heat treatment in the salt melt (KCl) affected the crystal structure, the size of coherent scattering regions, luminescence intensity, and lifetime. An increase of heat treatment temperature led to a reduction of luminescence intensity and lifetime due to the formation of point defects. The optimal synthesis conditions for obtaining the highest luminescence intensity of CaWO4:Nd3+ crystalline particles in salt melt were found to be the following Т1= 600 °C; t1=2 h (the stage of polymer gel thermal treatment), Т2= 800 °C; t2=1 h (the stage of thermal treatment in KCl salt melt). As-synthesized CaWO4:Nd3+ powders contain both coarse and fine fractions. However weak particle agglomeration allowed obtaining a water dispersion with individual nanoparticles (up to 200 nm) after ultrasonic treatment. According to the obtained results, the synthesized material is characterized by high luminescence intensity and high dispersion, and promising as fluorescent thermometers and biological labels.

Excellent electrical properties and the improved long-term stability of ZnO varistor ceramics were simultaneously achieved by doping NiO. The microstructural features were investigated using X-ray diffractometer, scanning electron microscopy, and energy dispersive spectroscopy, while the intrinsic point defects were characterized using frequency domain dielectric spectroscopy and verified by photoluminescence and Raman spectra. The results indicated that in the ZnO varistor ceramics, a reverse manipulation of donor point defects, i.e., suppressing mobile zinc interstitial but increasing stable oxygen vacancy, was achieved. The long-term stability of NiO-doped ZnO ceramics was improved via a decrease in zinc interstitial density, with a degradation rate of 0.064 μA cm−2 h−0.5. Meanwhile, due to an increase in oxygen vacancy density, the excellent nonlinear current–voltage performance, i.e., a high nonlinear coefficient (72.9), low leakage current density (0.08 μA cm−2), and low grain resistivity (13.43 × 10−3 Ω m), was maintained. The findings of this study provide a possible method for developing high-performance ZnO varistor ceramics by manipulating point defects.

In the present work, a phase-field model was developed to investigate the influence of recrystallization on bubble evolution during irradiation. Considering the interaction between bubbles and grain boundary (GB), a set of modified Cahn-Hilliard and Allen-Cahn equations, with field variables and order parameters evolving in space and time, was used in this model. Both the kinetics of recrystallization characterized in experiments and point defects generated during cascade were incorporated in the model. The bubble evolution in recrystallized polycrystalline of U–Mo alloy was also investigated. The simulation results showed that GB with a large area fraction generated by recrystallization accelerates the formation and growth of bubbles. With the formation of new grains, gas atoms are swept and collected by GBs. The simulation results of bubble size and distribution are consistent with the experimental results.

In this work, we performed molecular dynamics (MD) simulations on the interactions between a basal edge dislocation and point defects including vacancies and self-interstitial atoms in magnesium. Simulation results suggest that both self-interstitial atoms and vacancies have a blocking effect on dislocation motion, but the blocking effect of vacancies is much weaker than that of self-interstitial atoms. During interactions, self-interstitial atoms are absorbed and move with dislocation, and the edge dislocation climbs after absorbing self-interstitial atoms. In contrast, vacancies cannot be absorbed. To explain these observations, the binding energy and migration energy are calculated. The binding energy of both vacancies and self-interstitial atoms increases as they approach the dislocation core, seemingly indicating that they can be absorbed. However, the migration barrier of a vacancy is found to be about two orders in magnitude higher than that of a self-interstitial atom. Therefore, only self-interstitial atoms are absorbed, while vacancies cannot.

Summary Layered Li(Ni1−x−yCoxMny)O2 (NCM, with Ni ≥ 0.8) cathode materials are essential in achieving high energy densities in the next generation of lithium-ion batteries. To extend the materials' lifetime, it is necessary to understand the role played by crystal defects in the degradation during electrochemical cycling. In this study, NCM851005 (85% Ni) is investigated in the pristine state and after 100 and 200 cycles using scanning transmission electron microscopy, with the focus on the defects in the material. The formation of antiphase boundaries (APBs) from a dislocation in a pristine sample is proven. After 100 cycles, the APBs' length and width are enlarged compared with the pristine state. After 200 cycles, APBs further evolve into an intragranular rock-salt-like phase, distorting the nearby layered structure. It is suggested that the behavior of APBs plays a critical role in determining the performance of this cathode material with prolonged electrochemical cycling.

The capture efficiency describes the capability of a sink, such as a grain boundary (GB), dislocation, and void, to absorb point defects (PDs). The bias defines the difference in capture efficiency between the absorption of a vacancy and dumbbell at a sink. Complete kinetic information on PDs, including diffusion barriers and diffusion orientations, as well as accurate saddle points, are needed to determine the capture efficiency and bias at a sink accurately, which is computationally demanding. In the present study, the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) method was used to investigate the defect dynamics of PDs near different types of grain boundaries (GBs) (with both 〈100〉 and 〈110〉 families) accurately in body-centered cubic (BCC) iron (Fe). The capture efficiency, sink strength, and bias factor of different types of GBs were determined in Fe, which, different from traditional rate theory estimation, showed a distinct capture efficiency, sink strength, and bias in different GBs. The results demonstrate a strong positive correlation between the capture efficiency and the GB strain width, instead of the GB misorientation, GB energy, or GB-PD binding energy, which have been investigated previously. This work provides valuable insight into the radiation-induced microstructural evolution of GBs.

Profound and comprehensive investigations on the morphology characteristics of α precipitates are essential for the microstructural control of metastable β titanium alloys. At the very beginning of aging treatment, intragranular α precipitates with a dot-like morphology begin to generate nearby the dislocations, then those dot-like α precipitates with the same crystallographic orientation tend to connect with each other to develop a lath-like morphology. With the progress of aging treatment, the orientated lath-like α precipitates gradually combine with each other to form the V-shaped clusters or the triangular ones. The dislocations of { 1 1 ¯ 0 } β 11 1 ¯ > β edge type are evidenced within the β grains, and it is found that variant selection of α precipitates induced by the transformation strain and the interplay between α variants and the dislocations are confirmed as the key factors for the formation of the V-shaped or triangular clusters. The results of this work could provide underlying knowledge on the morphology characteristics of intraguranular α precipitates related to the crystal defects and the strain accommodation of α variants in metastable β titanium alloys.

In this study, we use differential phase contrast images obtained by scanning transmission electron microscopy combined with computer simulations to map the atomic electrostatic fields of MoS2 monolayers and investigate the effect of sulfur monovacancies and divancancies on the atomic electric field and total charge distribution. A significant redistribution of the electric field in the regions containing defects is observed, with a progressive decrease in the strength of the projected electric field for each sulfur atom removed from its position. The electric field strength at the sulfur monovacancy sites is reduced by approximately 50% and nearly vanishes at the divacancy sites, where it drops to around 15% of the original value, demonstrating the tendency of these defects to attract positively charged ions or particles. In addition, the absence of the sulfur atoms leads to an inversion in the polarity of the total charge distribution in these regions.

Zone-melted Bi2Te3-based alloys are the only commercially available thermoelectric (TE) materials, but they suffer from mediocre figure of merit (ZT) values and brittleness. In this work, we prepared Bi0.48Sb1.52Te3 sintered samples using a hot-pressing method and added tiny AgCuTe to improve the comprehensive properties. Because the carrier concentration is boosted by the AgCuTe addition, the bipolar effect at higher temperature is explicitly suppressed and the power factor is also improved in a broad temperature scope. Simultaneously, κlat is mostly diminished by the introduced phonon scattering centers comprising point defects, dislocations, and grain boundaries. Consequently, we achieved a ZTmax of 1.25 at 350 K and its average ZTave of 1.1 from 300 to 500 K in the (Bi0.48Sb1.52Te3 + 3 wt % Te) + 0.12 wt % AgCuTe sample. Composed of this sample and commercial Bi2Te2.5Se0.5, the fabricated TE module manifests a maximum power output density of 0.31 W cm-2 (Tcold = 300 K and Thot = 500 K). This work suggests that AgCuTe-doped Bi0.48Sb1.52Te3 is promising for recovering low-grade thermal energy near room temperature.

The use of two-dimensional (2D) materials in next-generation technologies is often limited by small lateral size and/or crystal defects. Here, we introduce a simple chemical strategy to improve the size and overall quality of 2D metal-organic chalcogenolates (MOCs), a new class of hybrid organic-inorganic 2D semiconductors that can exhibit in-plane anisotropy and blue luminescence. By inducing the formation of silver-amine complexes during a solution growth method, we increase the average size of silver phenylselenolate (AgSePh) microcrystals from 1 mm, while simultaneously extending the photoluminescence lifetime and suppressing mid-gap emission. Mechanistic studies using 77Se NMR suggest dual roles for the amine in promoting the formation of a key reactive intermediate and slowing down the final conversion to AgSePh. Finally, we show that amine addition is generalizable to the synthesis of other 2D MOCs, as demonstrated by the growth of single crystals of silver 4-methylphenylselenolate (AgSePhMe), a novel member of the 2D MOC family.

The nature of point defects in hexagonal boron nitride (hBN) is of current interest for the potential to alter its optical and electrical properties. The strong interaction between neutrons and the...

In the past few years remarkable interest has been kindled by the development of nonclassical light sources and, in particular, of single-photon emitters (SPE), which represent fundamental building blocks for optical quantum technology. In this Letter, we analyze the stability and electronic properties of an InSe monolayer with point defects with the aim of demonstrating its applicability as an SPE. The presence of deep defect states within the InSe band gap is verified when considering substitutional defects with atoms belonging to group IV, V, and VI. In particular, the optical properties of Ge as substitution impurity of Se predicted by solving the Bethe-Salpeter equation on top of the GW corrected electronic states show that transitions between the valence band maximum and the defect state are responsible for the absorption and spontaneous emission processes, so that the latter results in a strongly peaked spectrum in the near-infrared. These properties, together with a high localization of the involved electronic states, appear encouraging in the quest for novel SPE materials.

We found that two types of Cu-doped Bi2Te3 thin films fabricated by dissimilar sputter process had different microstructures and non-stoichiometries (Bi:Te ratios). We investigated the different levels of Te-vacancy ( V T e 2 + ) concentration in the films affected the point defects and the thermoelectric property of the films. The Cu additives were substituted for the Bi-sites (form C u B i 2 − defects) in case of a low Te-vacancy concentration ( V T e 2 + ) in the Bi2Te3 thin film. In the high V T e 2 + -defect concentration case, the C u B i 2 − -formation reaction was thought to be inhibited and evidences for the Cu-additive intercalating into a van der Waals layer (a C u v d W defect) were detected. We examined the lattice parameter, the thermoelectric properties, and the carrier transport properties of the two types of thin films with the different Te-vacancy concentrations as evidences for the different point defect formation characteristics between them. The Te-vacancy ( V T e 2 + ) dependency of the point defects formation ( C u B i 2 − or C u v d W ) in this system can suggest the clue to control an atomic scale Cu-site in n-type Cu doped Bi2Te3 thin films.

ZnO ceramics should have good mechanical properties to meet their applications in semiconductor industry. Based on experiments and the first principles, the effect of Mo doping on the microstructure and the mechanical properties of ZnO and AZO ceramics were studied, and the model of the effect of Mo doping on ZnO crystal defects was established. The results of the structures and fracture-surface morphology of different systems show that doping Mo atoms is beneficial for ZnO and AZO ceramics to eliminate the lattice defects, promote the grain growth and reduce the porosity at low doping concentration. However, when the doping concentration is too high, the new phase of Zn3Mo2O9 is formed and precipitated in 4MZO crystal. Correspondingly, the lattice distorted of doping systems is so serious that hinders the growth of grains and further affects the mechanical properties. Then, the bilinear stress-strain (σ-e) relationship was constructed by nanoindentation and finite element method. The results of mechanical properties by nanoindentation experiment and the first-principles simulation show that doping Mo can improve the hardness, elastic modulus, initial yield stress, plastic tangent modulus and creep resistance of ZnO and AZO ceramics. In particular, the mechanical properties of MZO ceramics are significantly improved because of the formation of Mo–O covalent bond between Mo6+ and O2−. In addition, it is worth noting that due to the synergistic and compensation effect of Al and Mo co-doped atoms, which is favor for reducing the lattice strain, improving the resistance to lattice deformation and forming the covalence of MAZO system, the mechanical properties of MAZO ceramics are increased remarkably.

The effects of a single point defect on InAs gate-all-around nanowire tunnel FETs (NW TFETs) are investigated. We considered two kinds of interfacial defects, the arsenic dangling bond (AsDB) and the arsenic antisite (AsIn). The critical physics related to the point defects, which are the charge trapping (CT), the trap-assisted tunneling, and their interplay, are rigorously captured using the full quantum transport model with the physical defect Hamiltonian obtained from the density functional theory calculations. We found that both defects on the NW cause the bandgap states, which crucially affects the TFETs performances. Through nonequilibrium Green’s function method self-consistently coupled with Poisson’s equation, the characteristics of the point defects under finite bias conditions are analyzed. We found that the CT is strong in AsIn, and thus the defect level, referenced to the valence band edge, is significantly changed by the gate bias. The strong CT leads to the screening of the gate field, which makes the defect level of AsIn effectively pinned near the drain Fermi level. The radial distributions of the density of states (DOS) and the phase relaxation time are analyzed. AsIn shows the strongly localized DOS at the defect center, while the DOS of AsDB is relatively delocalized due to the coupling with the valence bands. The impact of the defects on the TFET performances is examined as the gate length is scaled down. It is shown that AsIn acts as a limiting factor for scaling down of the TFETs.

Many rate theory models of cavity (void) swelling have been published over the past 50 years, all having the same, or similar, structures. A rigorous validation of the models has not been possible because of the dearth of information concerning the microstructures that correspond with the swelling data. Whereas the lack of microstructure information is still an issue for historical swelling data, in the past 10–20 years data have been published on the evolution of the microstructure (point defect yields from collision cascades, cavity number densities, and dislocation densities/yield strengths) allowing certain gaps in information to be filled when considering historic swelling data. With reasonable estimates of key microstructure parameters, a standard rate theory model can be applied, and the model parameter space explored, in connection with historical swelling data. By using published data on: (i) yield strength as a function of dose and temperature (to establish an empirical expression for dislocation density evolution); (ii) cavity number densities as a function of temperature; and (iii) freely migrating defect (FMD) production as a function of primary knock-on atom (PKA) spectrum, the necessary parameter and microstructure inputs that were previously unknown can be used in model development. This paper describes a rate-theory model for void swelling of 316 stainless steel irradiated in the EBR-2 reactor as a function of irradiation temperature and neutron dose.

Hybrid lead halide perovskites have reached comparable efficiencies to state-of-the-art silicon solar cell technologies. However, a remaining key challenge toward commercialization is the resolution of the perovskite device instability. In this work, we identify for the first time the mobile nature of bis(trifluoromethanesulfonyl)imide (TFSI-), a typical anion extensively employed in p-type dopants for 2,2'7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'spirofluorene (spiro-OMeTAD). We demonstrate that TFSI- can migrate through the perovskite layer via the grain boundaries and accumulate at the perovskite/electron-transporting layer (ETL) interface. Our findings reveal that the migration of TFSI- enhances the device performance and stability, resulting in highly stable p-i-n cells that retain 90% of their initial performance after 1600 h of continuous testing. Our systematic study, which targeted the effect of the nature of the dopant and its concentration, also shows that TFSI- acts as a dynamic defect-healing agent, which self-passivates the perovskite crystal defects during the migration process and thereby decreases nonradiative recombination pathways.

Current Li-ion batteries have a low energy density mainly because of the low Li intercalation level in graphite anodes. The high-density packing of lithium atoms in electrode materials amplifies th...

For more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems. Graphical abstract

Revealing the nature of intrinsic defects that act as charge-carrier trapping centers for persistent luminescence (PersL) in inorganic phosphors remains a crucial challenge from an experimental perspective. It was recently reported that Bi3+-doped LiREGeO4 (RE = Sc, Y, Lu) compounds displayed strong ultraviolet-A PersL at ∼360 nm with a duration of tens of hours at room temperature. However, the mechanistic origin of the PersL remains to be unveiled. Herein, we carried out a systematic study on optical transitions, formation energies, and charge-transition levels of dopants and intrinsic point defects in these compounds using hybrid density functional theory calculations. The results show that the efficient charging by 254 nm is due to the D-band transition of Bi3+ and hence the charge carriers pertinent to PersL are electrons originating from the dopants which are involved in the trapping and detrapping processes. The main electron-trapping centers are antisite defects GeLi0, interstitial defects Lii0, and dopants Bi2+, with the former one responsible for the strong PersL and the latter two for its long-time duration. These findings are further confirmed by comparison with calculated results for isostructural NaLuGeO4 and LiLuSiO4, based on which the roles of Li and Ge elements in forming intrinsic defects with appropriate trap depths for PersL are clarified. Our results not only assist in the understanding of experimental observations but also provide a theoretical basis for the rational design of novel PersL phosphors containing lithium and germanium in the host compound.

Dislocations have been identified to modify both the functional and mechanical properties of some ceramic materials. Succinct control of dislocation-based plasticity in ceramics will also demand knowledge about dislocation interaction with point defects. Here, we propose an experimental approach to modulate the dislocation-based plasticity in single-crystal SrTiO3 based on the concept of defect chemistry engineering, for example, by increasing the oxygen vacancy concentration via reduction treatment. With nanoindentation and bulk compression tests, we find that the dislocation-governed plasticity is significantly modified at the nano-/microscale, compared to the bulk scale. The increase in oxygen vacancy concentration after reduction treatment was assessed by impedance spectroscopy and is found to favor dislocation nucleation but impede dislocation motion as rationalized by the nanoindentation pop-in and nanoindentation creep tests.

In the frame of a quasi-viscous mechanism of plastic deformation via the flows of nonequilibrium point defects in the fields of local pressure gradients, peculiarities of propagation of the front of nanobands of crystal lattice reorientation are studied. A theoretical analysis of the velocities of point defects and the carriers of the rotational deformation mode – nanodipoles of partial disclinations, is made in terms of the type of point defects (vacancies and interstitial atoms), deformation temperature, disclination structure peculiarities and elastically stressed state at the nanoband propagation front. A possibility of simultaneous occurrence of the martensitic and quasi-viscous deformation modes at this front is shown. The effective viscosity coefficient is estimated for different energies of migration activation and temperatures. An important role of high local moments or stress field gradients is revealed during activation of the rotational deformation mode. It is shown that under the conditions of high local stress fields the material viscosity can reach the values close to that of liquid glass.

Site dependent light element doping in graphene can lead to exciting phenomenological prospects such as tunable bandgap, enhanced electron phonon coupling and anomalous transport properties for superconductivity, ferromagnetism and catalysis. However, they can lead to more additional defect sites and strain dependent effects as a residual fallout of the process and remains open to interpretations. In this work, we delineate a spectroscopic approach combined with ab-initio results to decipher these factors by using a prototypical in-situ boron doped reduced graphene oxide sample specimens and tuning them from low to moderate hole doping concentrations. The selectivity of doping configurations (BC3, BCO2 and BC2O) as well as their concentration is varied by regulating the annealing temperature (up to 1000 °C). We find a competitive relationship between the dopant and the residual surface oxygen atoms with gradual transformation of favorable doping configuration from out of plane to in-plane (substitutional) with increasing temperature. Furthermore, simultaneous induction of point defects and strain related effects in graphene lattice were also observed with increase in doping concentration. This led to anomalous bandgap crossover at high temperatures in boron doped graphene in comparison to the thermally reduced counterpart which could be important for electronic and transport applications.

PbNb2O6 (PN)-based piezoceramics are considered important materials used in high temperatures. Whereas, the main problem of PN-based ceramic is its low electrical performance such as piezoelectric constant (d33), severely restricting its practical applications. Here, based on the principle of regulating structure and performance via defect engineering, a new way of artificially tailoring point defects by A-site nonstoichiometry is implemented in this study. The results show that the PN-based ceramics with A-site deficiency exhibit significantly enhanced dielectric and piezoelectric properties. Particularly, the relative dielectric permittivity (er) increased by 165% (from 197 to 523) and the d33 increased by 177% (from 30 to 83 pC/N) while maintaining a high Curie temperature (TC ~ 543 °C), and the resultant superior comprehensive performance is nearly highest in PN-based ceramic system. The X-ray photoelectron spectrometer and Raman spectra reveal that A-site deficiency leads to a decreased level of oxygen vacancies and NbO6 octahedral distortion as well as disorderly motions of A-site cations, which further causes the markedly decreased domain size exhibited in piezoresponse force microscopy (PFM) images. Consequently, the improved domain structure gives rise to improved dielectric and piezoelectric properties. The results of this work provide a simple and effective strategy to improve the dielectric and piezoelectric properties while keeping a high TC in the PN-based ceramics system, meeting the urgent demands of high-temperature applications.

Quartz (trigonal, low-temperature α-quartz) is the most important polymorph of the silica (SiO2) group and one of the purest minerals in the Earth crust. The mineralogy and mineral chemistry of quartz are determined mainly by its defect structure. Certain point defects, dislocations and micro-inclusions can be incorporated into quartz during crystallisation under various thermodynamic conditions and by secondary processes such as alteration, irradiation, diagenesis or metamorphism. The resulting real structure is a fingerprint of the specific physicochemical environment of quartz formation and also determines the quality and applications of SiO2raw materials. Point defects in quartz can be related to imperfections associated with silicon or oxygen vacancies (intrinsic defects), to different types of displaced atoms, and/or to the incorporation of foreign ions in lattice sites and interstitial positions (extrinsic defects). Due to mismatch in charges and ionic radii only a limited number of ions can substitute for Si4+in the crystal lattice or can be incorporated in interstitial positions. Therefore, most impurity elements in quartz are present at concentrations below 1 ppm. The structural incorporation in a regular Si4+lattice site has been proven for Al3+, Ga3+, Fe3+, B3+, Ge4+, Ti4+, P5+and H+, of which Al3+is by far the most common and typically the most abundant. Unambiguous detection and characterisation of defect structures in quartz are a technical challenge and can only be successfully realised by a combination of advanced analytical methods such as electron paramagnetic resonance (EPR) spectroscopy, cathodoluminescence (CL) microscopy and spectroscopy as well as spatially resolved trace-element analysis such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and secondary-ion mass spectrometry (SIMS). The present paper presents a review of the state-of-the-art knowledge concerning the mineralogy and mineral-chemistry of quartz and illustrates important geological implications of the properties of quartz.

We have investigated the transmission of the 5 keV proton beam through a graphene sheet containing monovacancy, adatom, and Stone–Wales defects. The proton–graphene interaction potential was constructed using the Doyle–Turner's proton–carbon interaction potential. The closed form of the scattering law was obtained using the momentum approximation. Angular distributions of the transmitted protons were analyzed using the morphological method based on the inspection of the rainbow patterns in the impact parameter and scattering angle planes generated by the rainbow scattering. We have demonstrated that rainbows in the impact parameter plane are attracted and repelled by the nearest saddles and maxima of the reduced proton–graphene interaction potential. This explains why the rainbow pattern is so sensitive to the redistribution of the potential extrema caused by defects. Each defect type produces its distinctive rainbow pattern that dominantly determines the shape of the angular distribution. The ridge maxima of the angular distributions were investigated and related to the spectrum of the Jacobian matrix of the map generated by the scattering law. In the end, it has been shown how observed rainbow patterns could be used to determine the unknown defect densities of the complicated sample containing a combination of the different defect types.

Molecular dynamics simulation has become a powerful tool to deepen the understanding of the radiation damage mechanism of nuclear materials. Extracting point defects, analyzing their diffusion, and visualizing the defect dynamics in atomic simulation data are important, but challenging tasks to understand irradiation behavior. In the past, irradiation defects have been detected using the so-called Wigner–Seitz cell method and analyzed by the statistics of Frenkel pairs. However, traditional analysis modes blur the fine details of defect dynamics. In this paper, we present a visual analysis pipeline for domain scientists to comfortably explore radiation damage simulation data. We couple defect identification, defect clustering, molecule visualization, and tracking graph to form an integrated visual exploration approach. We describe the application of our approach in practice to study defect clustering in Ni–Fe alloy. With our proposed pipeline, defects can be extracted in a robust way, clusters can be visualized with a favorable representation, in-depth data analysis can be setup, and defect dynamics can be demonstrated in greater detail than previously possible.

Lead-free metal halide perovskites are environmentally friendly and have favorable electro-optical properties; however, their efficiencies are significantly below the theoretical limit. Using ab initio nonadiabatic molecular dynamics, we show that common intrinsic defects accelerate nonradiative charge recombination in CsSnI3 without creating midgap traps. This is in contrast to Pb-based perovskites, in which many defects have little influence on and even prolong carrier lifetimes. Sn-related defects, such as Sn vacancies and replacement of Sn with Cs are most detrimental, since Sn removal breaks the largest number of bonds and strongly perturbs the Sn-I lattice that supports the carriers. The defects increase the nonadiabatic electron-vibrational coupling and interact strongly with free carrier states. Point defects associated with I atoms are less detrimental, and therefore, CsSnI3 synthesis should be performed in Sn rich conditions. The study provides an atomistic rationalization of why lead-free CsSnI3 exhibits lower photovoltaic efficiency compared to some lead-based perovskites.

As an eco-friendly thermoelectric material, SnTe has attracted extensive attention. In this study, we use a stepwise strategy to enhance the thermoelectric performance of SnTe. Firstly, AgCl is doped into SnTe to realize band convergence and enlarge the band gap of AgCl-doped SnTe. AgCl-doping also induces dense point defects, strengthens the phonon scattering, and reduces the lattice thermal conductivity. Secondly, Sb is alloyed into AgCl-doped SnTe to further optimize the carrier concentration and simultaneously reduce the lattice thermal conductivity, leading to improved thermoelectric dimensionless figure of merit, ZT. Finally, (Sn0.81Sb0.19Te)0.93(AgCl)0.07 has approached the ZT value as high as ∼0.87 at 773 K, which is 272 % higher than that of pristine SnTe. This study indicates that stepwise AgCl-doping and Sb-alloying can significantly improve thermoelectric performance of SnTe due to synergistic band engineering, carrier concentration optimization and defect engineering.

Point-defect engineering is an effective way to control the mobility and transparent-conducting performance of sputtered fluorine-doped ZnO (FZO) thin films. In this study, doping with fluorine (F) is accomplished through a simple one-step deposition process and is demonstrated to enhance the crystal quality, eliminate the point defects, and boost the mobility as well as the performance of the films. Furthermore, the films’ characteristics are observed to be strongly dependent on F content. At the optimum F content of 1%, the FZO films exhibited the best crystal quality and the lowest concentration of Zn interstitial and O vacancy defects due to F passivation. Moreover, a mobility as high as 45.3 cm2/V and the greatest figure-of-merit performance are achieved for cutting-edge transparent electrode applications. However, a further increase of F content brought about an increased concentration of defects relating to Zn vacancies, especially F interstitials, which yielded the low mobility and poor performance due to the degraded structure.

(Ga0.5Li0.5)ZrO3 doped lead-free piezoceramics (Ba0.93Ca0.07)(Sn0.08Ti0.92)O3 {which was abbreviated as (1-x)BCST-xGLZ} were fabricated via traditional solid-state method. Microstructures and electrical properties of all samples were studied in detail using XRD, SEM, TEM, piezoelectric response, dielectric temperature spectrum, and ferroelectric hysteresis loop. Based on the experimental results, all the as-prepared samples possessed pure ABO3 perovskite structure. Single tetragonal (T) phase was obtained at x = 0 and 0.5 mol %, but the coexistence of orthorhombic-tetragonal (O-T) phase constructing MPB was obtained at 0.1 ≤ x ≤ 0.4 mol %. There was an initial increase in the grain size, which subsequently decreased. However, there was an initial reduction in the point defects (i.e., vacancies and pores, etc.), which then increased. The specimen possessed nanoscale lamellar domains and monocrystal structure at 0.2 mol %. All samples acquired good electrical property, especially for the sample at 0.2 mol %. It was confirmed that all specimens were relaxor ferroelectrics.

Silica-based optical fibers presents a variety of applications used in radiation environments such as space, fusion facilities, accelerators and nuclear power plants. The radiation-induced displacement damage in optical fibers resulting in point defects may lead to attenuation signals that is a major concern for these applications. The present study proposes a computational approach to the calculation of the proton-induced displacement damage in vitreous silica. Therefore, Geant4 as a Monte Carlo particle transport code has been used to obtain the knock-on atom distributions caused by the interaction of space trapped proton with vitreous silica during an ISS mission. Moreover, molecular dynamics simulations using ReaxFF potential have been performed to produce the initial vitreous silica structure to evaluate the displacement damage cascades by LAMMPS package. The results show that ReaxFF has an appropriate potential to produce and evaluate the vitreous silica structure that provides better agreement with experimental data at both short-range and medium-range order. Furthermore, ODC(Si3) and NBOHC(O1) are dominant defect species created in the vitreous silica after trapped proton irradiation, where the total number of defects have increased on average by 94 for each keV increasing in PKA energy approximately.

A model of two-component electromigration in a solid-state conductor with a substitutional impurity (an alloy of a type of a substitutional solid solution) is developed. The previously proposed approach to describe this process, using the methods of nonequilibrium thermodynamics, is generalized in this study in order to take into account the internal mechanical stresses arising as a result of mass transfer in the system. The dependence of the critical electromigration length on the effects caused by the interaction (correlation) of the fluxes of the conductor and impurity atoms is investigated. Practically important cases are considered in detail when electromigration processes prevail in the volume of a conductor or in the interface between a conductor and a protective dielectric. The influence of point crystal defects in a dielectric on the critical length of electromigration at the interface is analyzed. Estimates are given of the magnitude of the predicted effects of the influence of substitutional impurities on the electromigration of the intrinsic ions of the conductor. It is shown that, in the case of electromigration at interfaces, the correlational effects of the influence of substitutional impurities (up to the actual blocking of electromigration of conductor atoms) can be controlled by introducing nonequilibrium point defects into the protective dielectric layer.

Molecular dynamics (MD) is used to simulate cascade collision in gallium arsenide (GaAs) under different temperatures (300–900 K). During the entire simulation, the primary knock-on atom (PKA) is incident at a special angle, and its energy (EPKA) is within 10 keV. The simulation results are found to be reasonable based on the NRT equation and show that high EPKA causes direct damage, thereby increasing all evolution parameters such as the peak time (tp), steady time (ts), peak (Np) number, and steady (Ns) number of defects. Compared to EPKA, high temperatures reduce Ns of Frenkel pairs and increase the threshold displacement energy (Ed), during which Ga defects occupy the main part. It is also found that the difference between Ga and As vacancy-interstitial pairs on the amount makes tp of GaAs defects longer than AsGa defects, leading to a significant delay in antisite defects as temperature increases. Regarding clusters, high temperatures can promote the transformation of large clusters to isolated point defects for the vacancies, while only the transformation of large and small clusters is observed in the interstitials.

Planar perovskite solar cells (PSCs) have excellent photoelectric properties and show great commercialization potential. However, there are a lot of crystal defects in the perovskite films prepared by solution method, which reduces the development process of solar cells. In this work, alizarin red s (ARS) was doped into MAPbI3 films to passivate the defect. It was shown that the addition of ARS increased the quality of perovskite film and doped perovskite film exhibited improved light absorption. In addition, it was found that there was a strong interaction between ARS and perovskite, which reduced the density of defect states. The results showed that the passivated perovskite device had improved PL intensity, increased carrier lifetimes and reduced charge recombination. After passivation, the device obtained a higher open-circuit voltage (VOC) of 1.103 V where the control device was 1.055 V, and the best power conversion efficiency (PCE) of the doped device was 18.82%, which is 11.36% higher than that of the control device of 16.90%.

The deformation mechanisms and mechanical properties of Cu/Fe multilayer during compression process are investigated via atomistic simulations and rationalized analysis. It is found that yield stress and strain of Kurdjumov–Sachs model are lower than that of Nishiyama–Wassermann model, and lattice dislocation nucleates from periodic arrangement structures on the interface. We present that preferred slip systems are dominated not only by Schmidt factors but also by intersection line orientations of slip system on the interface, as well as angles between activated slip system of Cu layer and slip system of Fe layer. During deformation process, extended full dislocation dominates deformation behavior of Cu layer, and perfect dislocation and twinning dominate deformation behavior of Fe layer. After deformation, tetrahedral structures and point defects form on Cu side of interface and inside Fe layer, respectively. We calculate evolution curves for number of dislocation segments and interface thickness to illuminate deformation behavior.

The phase transformations and damping capacities in as solution-treated and 450 °C aged Ti49±xNi49∓xFe2 (x = 0 to 1) SMAs were investigated. In Ti48Ni50Fe2, Ti48.5Ni49.5Fe2 and Ti49Ni49Fe2 SMAs, no transformation occurred in the as solution-treated state, and B2 ↔ R1 transformation induced by Ti3Ni4 precipitates appeared when the SMAs were aged at 450 °C. DMA measurement showed that these as solution-treated SMAs exhibited strain glass behavior. The Ti49.5Ni48.5Fe2 specimen exhibited a two-stage B2 ↔ R2 ↔ B19′ transformation in the as solution-treated state, but after aging at 450 °C, the R2 ↔ B19′ was suppressed and B2 ↔ R1 appeared with B2 ↔ R2 remaining. The B2 ↔ R2 transformation is related to Fe, which causes point defects in the matrix. The Ti50Ni48Fe2 SMA showed a two-stage B2 ↔ R2 ↔ B19′ transformation in both solution-treated and 450 °C aged specimens. Microstructural observations showed Ti3Ni4 precipitates in Ti48Ni50Fe2, Ti48.5Ni49.5Fe2, Ti49Ni49Fe2 and Ti49.5Ni48.5Fe2 SMAs aged at 450 °C. The morphology and distribution of Ti3Ni4 precipitates are likely related to the amount of B2 ↔ R1 transformation.