Lattice Unit Cell Research Articles

Surface Reaction Induced Compressive Strain for Stable Inorganic Perovskite Solar Cells

AbstractCesium‐based inorganic perovskites have emerged as promising light‐harvesting materials for perovskite solar cells (PSCs) due to their promising thermal‐ and photo‐stability. However, obstacles to commercialization remain regarding their phase instability. In this work, we report a facile and effective strategy to regulate the surface compressive strain via in situ surface reaction to stabilize CsPbI3 perovskite. The use of a chelating ligand with a molecular configuration closely matching the integer multiples of the unit cell lattice parameters of CsPbI3 induces compressive strain at the surface of CsPbI3. The chemical bonding and strain modulation synergistically not only passivate film defects, but also inhibit perovskite phase degradation, thus significantly improving the intrinsic stability of inorganic perovskite. Consequently, enhanced power conversion efficiency (PCE) of 21.0 % and 18.6 % were respectively achieved in 0.16‐cm2 lab‐scale devices and 25.3‐cm2 solar modules. Further, surface reaction enables PSCs with enhanced thermal and operational stability; these devices retain over 95 % of their initial PCE after damp‐heat tests (i.e., in 85 °C and 85 % R. H. air) for 2000 h, and remain 99 % of their initial PCE after operating for 2000 h, representing one of the most stable inorganic PSCs reported so far.

Fin angles optimization of water-cooled plate-fin heat sink based on anisotropic Darcy–Forchheimer theory

Flat heat sinks are devices for efficient heat dissipation and are important components in manufacturing. For example, in precision glass molding, it is utilized as a cooling plate contributing to improve the quality of the product by reducing residual stress and shape deviation, during the gradual cooling phase. In this study, we attempted to achieve precise temperature design of the cooling plate using variable lattice optimization. Fins allow for controlling the flow direction and achieving efficient heat transfer. Therefore, elliptical cylindrical fins were adopted as lattice unit cells, increasing the design freedom of the flow field. To account for the asymmetric flow field within the unit cell, we introduced an asymmetric tensor for the coefficients of the effective physical properties in the Darcy–Forchheimer equation. The proposed method's effectiveness and validity are discussed through numerical calculations with effective material properties, reproduced detailed shapes, and experimental verification. The optimization aiming to minimize the average temperature yielded a numerical simulation temperature decrease of 24.6 % and an experimental temperature decrease of 14.1 % compared to the benchmark model.

Double-foci acoustic metamaterial Luneburg lens

In this study, an acoustic Luneburg lens is proposed to achieve double foci. High energy density between the two foci can be obtained, which enables the realization of an ultra long acoustic jet between the two foci. The acoustic Luneburg lens is designed based on the gradient index acoustic metamaterial with lattice unit cells. Analytical and numerical analyses were performed to investigate the performance of double foci Luneburg lens. Results show that the double foci can be realized with acoustic jet length goes up to 30 times compared with the wavelength, which has multiple potential applications in medical imaging and energy harvesting.

Impact of lattice structure on compressive performance and strength to weight ratio in continuous stereolithography

Lattice structures have emerged as a creative solution in additive manufacturing to achieve lightweight structures. Lattices offer the capability to reduce material usage, production costs, and weight while maintaining the structural integrity of a part. Due to its rise in popularity and excellent properties, lattice structures have been used in many applications, including but not limited to aerospace, bioengineering, and acoustics. This study aimed to explore the performance of different types of lattices on 3D additive manufactured parts by varying the type of unit cell. The three unit cells that were compared are body-centered cubic (BCC), face-centered cubic (FCC), and Fluorite. The lattice’s strength-to-weight ratio of different lattice unit cells when subjected to compression forces was evaluated. BCC and FCC have had considerable research while Fluorite has had far less research. This study aims to contribute new knowledge on the less studied Fluorite unit cell. The selected lattice structures were printed using continuous stereolithography (CSLA). This 3D printing process utilizes a photopolymerization reaction to solidify liquid resin layer by layer. Through this study, Fluorite demonstrated the highest strength-to-weight ratio among the three lattice structures examined, averaging 19,377 Nm/kg over five samples. Its potential for applications requiring high strength requirements is highlighted by this finding. Alternatively, BCC lattice structures had the weakest strength-to-weight ratio but exhibited remarkable structural resilience to deformation. The BCC lattice structures showed a more significant deformation before failure. Fluorite lattice structures are more suitable for high-strength applications, while BCC lattice structures can be used where high strength is not a primary parameter. This research aimed to determine the optimal lattice unit cell to implement in future choices in additive manufacturing applications.

Exploring the Impact of Elevated Pressure on the Structural Dynamics of TlInS2 Crystal (I): A First-Principles Investigation with XRD, Raman, and Hirshfeld Topology

The structural dynamics of Thallium Indium Disulfide (TlInS2) crystal under elevated pressures were comprehensively investigated using a combination of X-ray diffraction (XRD), Raman spectroscopy via first-principles calculations, and Hirshfeld surface (HS) analysis. This study aims to elucidate pressure-induced modifications in the crystal structure and their associated properties of TlInS2 crystal. The findings reveal significant structural transformations as pressure increases, with XRD patterns indicating lattice compression and a critical transition from semiconductor to conductor at pressure P=6.25GPa [42]. The calculations predict a reduction in bond lengths, specifically S1-In1 and S1-Tl2, alongside a corresponding decrease in lattice parameters and unit cell volume. Raman spectroscopy corroborates these changes through shifts in phonon modes. The HS analysis provides further insights into pressure-dependent alterations in intermolecular interactions, revealing changes in voids and surface characteristics. The data gained from TlInS2's structural behavior under pressure, contributing to the optimization of its functional properties for pressure-tunable applications in high-performance electronic and optoelectronic devices.

Comparison Study Between Inherited and Biogenic Calcium Carbonate Formation on The Surface Roots of Eucalyptus Trees Using X-Ray Technique and Field Observations

Background: This study aims to explain the mechanism of formation of calcite and it's to shed light on the synthetic carbonate crystallization on the surface of roots due to this mechanism is poorly understood and highly controversial. It is accepted that calcite formed originally from parent rocks and not in soils. Method: The origin of calcite in calcareous soil, in Aldiwaniya city, Iraq was investigated, by selecting two soil samples, one from the contact zone with root surface and the other sample from bulk soil and out of the root system. Results: X-ray diffraction showed that the calcite has two types, first one is well crystallized and ordered, with only minor deviations in lattice unit cell parameters relative to typical calcite. The clay-sized calcite (active calcite) is enriched in A and C-horizons relative to biogenic calcite and this mineral exist in larger size separates, and it's clearly appears in the shape of white crystals around eucalyptus root surfaces as shown in graphs. The results of X-ray showed that the appearance of smectite mineral which was diagnosed by the peak 14.21 A° in air dry magnesium-saturated treatment which expanded to 16.28 A° when saturated with ethylene glycol, where clarity of peak was increased, Also, the results showed that the appearance of peak 14.21 A° in magnesium saturation air dried, as a shoulder on the peak of the mica (10.14 A°). Conclusion: In general, calcite minerals have characteristic x-ray diffraction peaks at the following angles: 29.5, 31.7, 34.5, 35.7, 47.3, 56.4, and 63.4 degrees.

High-pressure synthesis, crystal structure and anisotropic thermal/compressive behaviors of pseudo-ternary (V,Cr,Mo)P4

Pseudo-ternary CrP4-type (V,Cr,Mo)P4 was successfully synthesized at the conditions of 4 GPa and 900 °C by using a large volume multi-anvil-type press. SEM-EDS and STEM analyses revealed that the synthesized pseudo-ternary (V,Cr,Mo)P4 contains almost equimolar amounts of transition metals. The lattice parameters and unit cell volume of (V,Cr,Mo)P4 yield the average value of its end-members. The low-temperature (133 K–333 K) in-situ synchrotron XRD measurements demonstrated that the c-axis showed the highest coefficient of thermal expansion, followed by the b-axis and the a-axis. These thermal behaviors are the same as the binary end-members and pseudo-binary (V,Cr)P4. While from the high-pressure (P < 10 GPa) in-situ synchrotron XRD measurements, it was found that (V,Cr,Mo)P4 showed no phase transition and compression behaviors in which the c-axis was more compressible than the other two axes (b and a) and the b-axis was slightly compressible more than the a-axis. The zero-pressure bulk modulus of 106 (1) GPa and 122.1 (7) GPa were obtained for (V,Cr)P4 and (V,Cr,Mo)P4, respectively. MoP6 octahedral is highly distorted in comparison with VP4 and CrP4, thus the incorporation of MoP4 greatly yields incompressible behaviors of CrP4-type phosphides with respect to temperature and pressure.

Three-dimensional free-standing heterostructures out of MoS2 and rGO with infused PDMS towards electromechanical pressure sensing

Abstract The behavior of two-dimensional (2D) materials constructed as three-dimensional structures is studied to bring such materials one step closer to the real-life application. Lattices structures of gyroid triply periodic minimal surface (TPMS) were fabricated out of 2D materials, namely, molybdenum disulfide (MoS2), and reduced graphene oxide (rGO), forming for the first time free-standing MoS2 (FSM) lattice and free-standing hetero-structural lattice of MoS2 and rGO (FSH) out of TPMS. These 2D materials were also integrated with polydimethylsiloxane (PDMS) elastomer, forming FSM/PDMS and FSH/PDMS composites. Mechanical characterization, including compression and cyclic tests, were conducted on FSM, FSH, and the composites. Additionally, electromechanical characterization was conducted to evaluate the sensing potential of these structures. It is worth noting that the elastic modulus of the 10 unit-cells with either FSM or FSH was higher than the other lattices of the same type. FSH tends to have a higher modulus at 1504.4 kPa in the 10 unit-cells. This modulus is even higher at 3 MPa when PDMS is added to the FSH lattice. Due to the brittle fracture, FSM or FSH lattices follow the layer-by-layer failure mechanism. Samples with PDMS are more stable towards such cyclic tests without noticeable failures or a decrease in elastic modulus. Finally, the 10 unit-cell lattices of FSH/PDMS composite have the highest conductivity at 2.5 mA, and a comparable sensitivity at 0.365 kPa−1 over the range of 0–100 kPa.

Effect of the chemical substitution on structural parameters and microwave properties of the Co–Ni–Zn spinels

Co0.3Ni0.7-xZn xFe2O4 (where x = 0.00–0.7 with step 0.1) spinels or CNZF with constant Co concentration and varying of the Ni/Zn concentration were obtained by the ceramic method from initial oxides. Based on X-ray diffraction data it was concluded that all samples are single-phase (SG: Fd-3m). Concentration dependences of the lattice constant and unit cell volume correlate well with Vegard's rule and the average value of the Zn2+ and Ni2+ ionic radii. The microwave permeability was measured in the frequency range of 0.1–20 GHz by a coaxial technique. Two resonances on frequency dependences were observed. Analysis of the microwave properties and magnetostatic data showed that low-frequency magnetic peak was caused by a resonance of domain boundaries; high-frequency peak was due to a natural ferrimagnetic resonance. Obtained results opens broad perspectives for practical application of such kind of materials and possibility for microwave parameters control by the external magnetic field.

Superior damage tolerance observed in interpenetrating phase composites composed of aperiodic lattice structures

Interpenetrating Phase Composite (IPC) metamaterials, based on lattice topologies, have garnered significant attention as advanced materials for structural applications. However, conventional IPCs, which rely on periodic lattice unit cells, are prone to catastrophic failure due to their global deformation modes. To overcome this limitation, we present a novel IPC design utilizing aperiodic truss unit cells, inspired by the elusive “Einstein” monotile pattern. Our concept is demonstrated through IPC 3D printed via polymer jetting, using a hard polymer as the lattice filler and a soft polymer as the matrix. The distinctive mechanical properties of IPCs are characterized through single and cyclic quasi-static compression testing. Our findings demonstrate that aperiodic IPCs enable progressive deformation with gradual compression stress plateaus. Additionally, aperiodic IPCs exhibit remarkable damage tolerance, retaining 67.59 % of residual energy absorption and 73.83 % of ultimate strength after multiple cyclic compressions up to 30 % strain. These mechanisms are attributed to the synergistic deformation of interconnected unit cells, which lead to self-adjusting plastic collapse, progressive displacement evolution and delocalized deformation. This aperiodic concept paves the way for developing high-performance cushioning protection materials.

Surface Reaction Induced Compressive Strain for Stable Inorganic Perovskite Solar Cells.

Cesium-based inorganic perovskites have emerged as promising light-harvesting materials for perovskite solar cells (PSCs) due to their promising thermal- and photo-stability. However, obstacles to commercialization remain regarding their phase instability. In this work, we report a facile and effective strategy to regulate the surface compressive strain via in-situ surface reaction to stabilize CsPbI3 perovskite. The use of a chelating ligand with a molecular configuration closely matching the integer multiples of the unit cell lattice parameters of CsPbI3 induces compressive strain at the surface of CsPbI3. The chemical bonding and strain modulation synergistically not only passivate film defects, but also inhibit perovskite phase degradation, thus significantly improving the intrinsic stability of inorganic perovskite. Consequently, enhanced power conversion efficiency (PCE) of 21.0% and 18.6% were respectively achieved in 0.16-cm2 lab-scale devices and 25.3-cm2 solar modules. Further, surface reaction enables PSCs with enhanced thermal and operational stability; these devices retain over 95% of their initial PCE after damp-heat tests (i.e., in 85 ℃ and 85% R.H. air) for 2000 h, and remain 99% of their initial PCE after operating for 2000 h, representing one of the most stable inorganic PSCs reported so far.

Influence of electron and hole doping on structural, Magnetic, and magnetocaloric properties of Ba2FeMoO6 double perovskite

The impact of Sm3+ and Ag+ doping at the Ba2+ site on the structural, magnetic, and magnetocaloric properties of Ba2FeMoO6 (BFMO) double perovskite was compared. Samples were synthesized using the sol–gel method. Rietveld refinement patterns of samples Ba2-xAxFeMoO6 (A=Sm, Ag, x = 0.0, 0.025) showed all samples had cubic structures with Fm-3 m space group and no impurity. The lattice parameters and unit cell of the Ba1.975Sm0.025FeMoO6 (BSFMO), and Ba1.975Ag0.025FeMoO6 (BAFMO) samples decreased compared to the parent sample. X-ray photoelectron spectroscopy confirmed that Fe and Mo ions were mixed valence for all samples. The results of magnetization versus temperature (M−T) showed an increase for BSFMO and a decrease for BAFMO samples under an external magnetic field of 0.05 T. The magnetic study indicated a decrease in the transition temperature for BSFMO (∼303 K) and an increase for BAFMO (∼321 K) to compare with the parent sample (∼310 K). The maximum value of magnetic entropy changes (ΔSMmax)of the BFMO, BSFMO, and BAFMO samples at H=3 T obtained 0.92 Jkg-1K−1, 0.75 Jkg-1K−1, and 0.39 Jkg-1K−1, respectively, and the second-order magnetic phase occurred around the transition temperature. For BFMO, BSFMO, and BAFMO, the relative cooling power (RCP) is 34.48 J/kg, 32.25 J/kg, and 21.97 J/kg, respectively. The second-order magnetic phase transition occurred around the transition temperature for all samples using the energy criterion as well as the universal curve method. In addition, we used Widom’s law to determine the critical exponent of the samples, which provides a new thermodynamic method to determine the magnetic phase transition. The results of the magnetocaloric effect indicate that although the maximum entropy changes and relative cooling decrease with doping Ag and Sm ions, they have a wide temperature range of magnetic entropy changes compared to the pristine sample, which can be candidates for magnetic cooling.

Density functional theory study of influence of impurity defects on structure and properties of cassiterite

Using density functional theory (DFT), geometric optimizations were performed on the supercell systems of undoped cassiterite and 24 types of doped cassiterite with metals such as Sc, Ti, V, etc. The lattice constants, band structures, and electronic density of states (DOS) were calculated to investigate the crystal structure and electronic properties of cassiterite. The results indicate that the presence of impurity defects leads to varying degrees of distortion in the lattice angles and unit cell of cassiterite crystal. Doping with Ti and Al increases the semiconductor band gap of cassiterite, while other impurity-doped cassiterite decreases the band gap. The impurity-doped cassiterite band gap gradually decreases with increasing atomic number, exhibiting semiconductor-to-metal transition in the doped cassiterite. The overall DOS of cassiterite doped with Nb, Mo, Ta, W, As, Sb and Bi shifts to the direction of low energy, and the oxidation capacity of cassiterite is enhanced.

In situ study of atomic clustering in Fe-19 Ga type alloy

The results of high-precision electro-resistivity measurements, ρ(T), for Fe-18.5%Ga alloy over a wide temperature range are presented. An anomaly in the ρ(T) temperature behavior is detected and it is proved that it correlates well with the change in the unit cell lattice parameter of the alloy and with the results obtained from measuring magnetization, dilatometry and positron annihilation. From the neutron diffraction data, it follows that the detected anomaly is associated with the formation of a cluster-like microstructure of the alloy: in the structurally disordered A2 matrix, regions with partially ordered D03 phase are formed. Interpretation of this non-monotonic behaviour of ρ(T) is discussed.

Study on the structure, Mössbauer spectroscopy, and magnetic properties of Sr1-xYxFe12O19 hexaferrites

The Sr1-xYxFe12O19 (x =, 0.05, 0.1, 0.15) series hexagonal ferrite samples were successfully prepared by the sol-gel method. X-ray diffraction (XRD) showed that Y3+ successfully replaced Sr2+ sites, resulting in a reduction of lattice parameters and unit cell volume. Mössbauer spectral analysis showed that Y3+doping caused the conversion of some Fe3+ to Fe2+ at the 2a site, resulting in a decrease in the average hyperfine field of the doped samples. Vibrating sample magnetometer (VSM) measurements indicated that with increasing Y3⁺ content, the saturation magnetization of the samples decreased, while the coercivity significantly increased. Notably, at a doping level of x = 0.05, the sample exhibited a coercivity of 4798.09 Oe, representing a 99.11% increase compared to the undoped sample, while the saturation magnetization only decreased by 3.24%.

Water Effect on the Electronic Properties and Lithium-Ion Conduction in a Defect-Engineered LiFePO4 Electrode

Defect-engineering accelerates the conduction of lithium ions in the cathode materials of lithium-ion batteries. However, the effects of defect-engineering on ion conduction and its mechanisms in humid environments remain unclear in the academic discourse. Here, we report on the effect of vacancy defects on the electronic properties of and Li-ion diffusion in a LiFePO4 material in humid environments. The research findings indicate that vacancy defects reduce the lattice constant and unit cell volume of LiFePO4. Additionally, the water molecules occupy the Li-ion vacancies, leading to an increase in the lattice constant of LiFePO4. The computational results of the electronic properties show that the introduction of water molecules induces a transition in LiFePO4 from a semiconductor to a metallic behavior, with a transfer of 0.38 e of charge from the water molecules to LiFePO4. Additionally, the migration barrier for Li ions in the H2O + LiFePO4 system is found to be 0.50 eV, representing an 11.1% increase compared to the pristine LiFePO4 migration barrier. Our findings suggest that water molecules impede the migration of Li ions and provide important insights into the effect of defect-engineering on electronic properties and ion conduction under humid conditions.

The thermal expansion of Ti-substituted CaAl12O19

CaAl12O19, which can incorporate Ti as both Ti3+ and Ti4+ (charge coupled substitution with Mg2+), is one of the first minerals to condense from a gas of solar composition and is used as a ceramic. It is variously known as hibonite, calcium hexaluminate (CaO.6Al2O3), and CA6. The lattice parameters and unit cell volumes of Ti-substituted hibonite (P63/mmc) with the formulae CaAl11.8Ti3+0.2O19 and CaAl9.8Ti3+0.54Mg0.83Ti4+0.83O19 were determined as a function of temperature from ~ 10 to 275 K by neutron powder diffraction. The thermal expansion is highly anisotropic with the expansion in c a factor of ~ 5 greater than that in a. The change in a is approximately equal for the two compounds whereas the change in c is almost 50% larger for CaAl11.8Ti3+0.2O19. CaAl11.8Ti3+0.2O19 also exhibits negative thermal expansion between 10 and 70 K. The change in unit cell volume with temperature of both compositions is well described by a two term Einstein expression. The large change in c is consistent with substitution of Ti onto the M2 and M4 sites of the R-block structural unit.

Energy Absorption of a Novel Lattice Structure‐Filled Multicell Thin‐Walled Tubes Under Axial and Oblique Loadings

Multicell design and lattice structure as filling material are two effective methods for enhancing the energy absorption performance of thin‐walled tubes. This study combines these two approaches to present a multicell tube with a novel lattice structure and investigates the energy absorption performances of these hybrid multicell tubes under axial (0°) and oblique (10°, 20°, and 30°) impact loading conditions. As filling structure, β‐Ti3Au lattice geometry with varying lattice strut diameters and the number of lattice unit cells are used, while the single and multicell thin‐walled tubes with different tube thicknesses are employed as main absorbing element. In this context, the effects of numbers of lattice unit cells, lattice strut diameter, cell numbers of the tube, and tube thickness on energy absorption performance of hybrid tubes are examined using validated nonlinear finite element models. This investigation unveils that the synergistic interplay between the multicell tubes and lattice structure during deformation significantly elevates the energy absorption performance of the hybrid structure. Notably, the findings demonstrate that multicell hybrid tubes exhibit a remarkable capacity to absorb up to 30.36% more impact energy compared to the aggregate absorption of individual components in hybrid tubes.

Physicochemical, morphological, and charge carrier mobility range dielectric evaluations of Yb-doped BaCo2 W-type hexagonal ferrites for high-frequency applications

Microwave absorption materials have attracted attention due to their extensive applications in different fields. Herein, ytterbium-doped BaCo2 W-type hexaferrite nanocrystallites with a nominal composition of BaCo2YbxFe16−xO27 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were synthesized via the sol–gel method, and their physicochemical and dielectric characteristics were estimated. XRD plots revealed the pure phase structure of each prepared hexaferrite sample. The lattice constant and unit cell volume were affected by changes in the Yb concentration. The crystallite size was measured by the Debye–Scherrer formula, revealing intense crystals typically in the 18–33 nm range. FTIR spectroscopy showed multiple absorption bands from 430 to 3000 cm−1, and Raman spectroscopy revealed multiple peaks between 200 and 1000 cm−1, displaying the allocated polyhedra and symmetry. XPS spectroscopy confirmed the existence of all metal ions in the required valence state. The dielectric measurements were evaluated at frequencies from 1 to 6 GHz for all the synthesized compositions, and the material behavior was explained using the Maxwell–Wagner and Koop theories. The conduction mechanism in the hexagonal ferrites was assessed using Cole–Cole analysis. Reflection loss measurements were also conducted: the samples at x = 0.03 and x = 0.12 yielded minimal reflection losses of −60.06 and −51.69 dB at 5.5 GHz, respectively. The results demonstrate the suitability of the samples for use in microwave and high-frequency absorption applications.

Directional Acoustic Bulk Waves in a 2D Phononic Crystal

We used the transfer matrix method to investigate the conditions supporting the existence of directional bulk waves in a two-dimensional (2D) phononic crystal. The 2D crystal was a square lattice of unit cells composed of rectangular subunits constituted of two different isotropic continuous media. We established the conditions on the geometry of the phononic crystal and its constitutive media for the emergence of waves, which, for the same handedness, exhibited a non-zero amplitude in one direction within the crystal’s 2D Brillouin zone and zero amplitude in the opposite direction. Due to time-reversal symmetry, the crystal supported propagation in the reverse direction for the opposite handedness. These features may enable robust directional propagation of bulk acoustic waves and topological acoustic technology.