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Showing papers on "Tetragonal crystal system published in 2020"


Journal ArticleDOI
TL;DR: The results suggest that rare-earth intermetallics with highly symmetric crystal lattices may ubiquitously host nanometric skyrmions of exotic origins, which are potentially suitable for the design of high-density information bits.
Abstract: Magnetic skyrmions are topologically stable spin swirls with a particle-like character and are potentially suitable for the design of high-density information bits. Although most known skyrmion systems arise in non-centrosymmetric systems with a Dzyaloshinskii–Moriya interaction, centrosymmetric magnets with a triangular lattice can also give rise to skyrmion formation, with a geometrically frustrated lattice being considered essential in this case. Until now, it remains an open question if skyrmions can also exist in the absence of both geometrically frustrated lattice and inversion symmetry breaking. Here we discover a square skyrmion lattice state with 1.9 nm diameter skyrmions in the centrosymmetric tetragonal magnet GdRu2Si2 without a geometrically frustrated lattice by means of resonant X-ray scattering and Lorentz transmission electron microscopy experiments. A plausible origin of the observed skyrmion formation is four-spin interactions mediated by itinerant electrons in the presence of easy-axis anisotropy. Our results suggest that rare-earth intermetallics with highly symmetric crystal lattices may ubiquitously host nanometric skyrmions of exotic origins. Experimental realizations of magnetic skyrmions, particle-like spin swirls with topological protection, so far have required inversion symmetry breaking or a geometrically frustrated lattice. In centrosymmetric GdRu2Si2, in which a geometrically frustrated lattice is absent, a skyrmion lattice phase emerges, which is probably stabilized by four-spin interactions mediated by itinerant electrons in the presence of easy-axis anisotropy.

158 citations


Journal ArticleDOI
24 Mar 2020
TL;DR: D density functional theory was used to determine the structural, electronic, and optical properties of the cubic, tetragonal, and orthorhombic temperature-dependent phases of CsPbBr3 perovskite using the full-potential linear augmented plane wave method.
Abstract: Cesium lead bromide (CsPbBr3) perovskite has recently gained significance owing to its rapidly increasing performance when used for light-emitting devices. In this study, we used density functional...

87 citations


Journal ArticleDOI
TL;DR: Insight is provided into the role of electrodes on the performance of hafnium oxide-based ferroelectrics, mechanisms driving wake-up and fatigue, and a non-destructive means to characterize the phase changes accompanying polarization instabilities are demonstrated.
Abstract: Ferroelectric hafnium zirconium oxide holds great promise for a broad spectrum of complementary metal-oxide-semiconductor (CMOS) compatible and scaled microelectronic applications, including memory, low-voltage transistors, and infrared sensors, among others. An outstanding challenge hindering the implementation of this material is polarization instability during field cycling. In this study, the nanoscale phenomena contributing to both polarization fatigue and wake-up are reported. Using synchrotron X-ray diffraction, the conversion of non-polar tetragonal and polar orthorhombic phases to a non-polar monoclinic phase while field cycling devices comprising noble metal contacts is observed. This phase exchange accompanies a diminishing ferroelectric remanent polarization and provides device-scale crystallographic evidence of phase exchange leading to ferroelectric fatigue in these structures. A reduction in the full width at half-maximum of the superimposed tetragonal (101) and orthorhombic (111) diffraction reflections is observed to accompany wake-up in structures comprising tantalum nitride and tungsten electrodes. Combined with polarization and relative permittivity measurements, the observed peak narrowing and a shift in position to lower angles is attributed, in part, to a phase exchange of the non-polar tetragonal to the polar orthorhombic phase during wake-up. These results provide insight into the role of electrodes in the performance of hafnium oxide-based ferroelectrics and mechanisms driving wake-up and fatigue, and demonstrate a non-destructive means to characterize the phase changes accompanying polarization instabilities.

70 citations


Journal ArticleDOI
TL;DR: Repetitive electrical pulse stimulation of blue-phase liquid crystals promotes their reconfiguration into stable non-cubic structures with promising electro-optical responses for display technologies.
Abstract: Natural self-assembled three-dimensional photonic crystals such as blue-phase liquid crystals typically assume cubic lattice structures. Nonetheless, blue-phase liquid crystals with distinct crystal symmetries and thus band structures will be advantageous for optical applications. Here we use repetitive electrical pulses to reconfigure blue-phase liquid crystals into stable orthorhombic and tetragonal lattices. This approach, termed repetitively applied field, allows the system to relax between each pulse, gradually transforming the initial cubic lattice into various intermediate metastable states until a stable non-cubic crystal is achieved. We show that this technique is suitable for engineering non-cubic lattices with tailored photonic bandgaps, associated dispersion and band structure across the entire visible spectrum in blue-phase liquid crystals with distinct composition and initial crystal orientation. These field-free blue-phase liquid crystals exhibit large electro-optic responses and can be polymer-stabilized to have a wide operating temperature range and submillisecond response speed, which are promising properties for information display, electro-optics, nonlinear optics, microlasers and biosensing applications.

68 citations


Journal ArticleDOI
TL;DR: In this paper, tetragonal prismatic γ-In2Se3 nanoparticles with predominantly exposed {110} facets are synthesized hydrothermally in the presence of ethylenediaminetetraacetic acid (EDTA).
Abstract: Crystals grown in the direction of high-energy facets have reduced surface energy, a small portion of high-energy crystal facets, and high photocatalytic activity. In this work, γ-In2Se3 nanoparticles with predominantly exposed {110} facets are synthesized hydrothermally in the presence of ethylenediaminetetraacetic acid (EDTA). EDTA plays a key role in regulating the exposed {110} facets and by adding 0.04 M of EDTA, tetragonal prismatic γ-In2Se3 nanoparticles with the {110} facets are produced. Studies of the photocatalytic activity of tetracycline (TC) reveal that the tetragonal prismatic γ-In2Se3 prepared with 0.04 M EDTA has the optimal activity that is about 1.9 times higher than that of conical γ-In2Se3 prepared without EDTA. The capture experiments show that h+ and O 2− affect degradation of TC and our results reveal a novel strategy to synthesize γ-In2Se3 with the optimal morphology and photocatalytic activity.

63 citations


Journal ArticleDOI
TL;DR: This work provides insights into the thermodynamic driving force of the instabilities and will help guide computer simulations and experimental synthesis in material screening, and obtain phonon-stable structures for each composition.
Abstract: Metal halide perovskites are promising candidates for next-generation photovoltaic and optoelectronic applications. The flexible nature of the octahedral network introduces complexity when understanding their physical behavior. It has been shown that these materials are prone to decomposition and phase competition, and the local crystal structure often deviates from the average space group symmetry. To make stable phase-pure perovskites, understanding their structure-composition relations is of central importance. We demonstrate, from lattice dynamics calculations, that the 24 inorganic perovskites ABX3 (A = Cs, Rb; B = Ge, Sn, Pb; X = F, Cl, Br, I) exhibit instabilities in their cubic phase. These instabilities include cation displacements, octahedral tilting, and Jahn-Teller distortions. The magnitudes of the instabilities vary depending on the chemical identity and ionic radii of the composition. The tilting instabilities are energetically dominant and reduce as the tolerance factor increases, whereas cation displacements and Jahn-Teller type distortions depend on the interactions between the constituent ions. We further considered representative tetragonal, orthorhombic, and monoclinic perovskite phases to obtain phonon-stable structures for each composition. This work provides insights into the thermodynamic driving force of the instabilities and will help guide computer simulations and experimental synthesis in material screening.

60 citations


Journal ArticleDOI
TL;DR: In this article, the authors have shown that Amino acids have properties like molecular chirality and zwitter ionic nature helps to improve NLO properties of ADP.

59 citations


Journal ArticleDOI
TL;DR: In this paper, a single-phase white-light-emitting YPO4 phosphor, single and co-doped with Dy3+/Eu3+, aiming at UV-pumping in WLEDs, was successfully produced.

51 citations


Journal ArticleDOI
TL;DR: This work reports the observation of antiskyrmions in a second inverse tetragonal Heusler compound, Mn2Rh0.95Ir0.05Sn, which can be formed stoichiometrically without any Mn vacancies and which thus exhibits a much smaller magnetization.
Abstract: Recently, magnetic antiskyrmions were discovered in Mn1.4Pt0.9Pd0.1Sn, an inverse tetragonal Heusler compound that is nominally a ferrimagnet, but which can only be formed with substantial Mn vacan...

50 citations


Journal ArticleDOI
TL;DR: In this article, the La-substitution effects for Bi3+-site in 0.7Bi1.03(1-x)LaxFeO3-0.3BaTiO3 (abbreviated as BF30BT-100xLF with x = 0.00, 0.01, 0.,035, 0,07 and 0.10) ceramics were investigated systematically.

46 citations


Journal ArticleDOI
TL;DR: In this paper, the thermal stability and crystallization mechanism of Zr59.3Cu28.8Al10.4Nb1.5 (at%) metallic glass produced through selective laser melting SLM (from industrial grade material) was studied and compared with the same alloy produced by suction casting.

Journal ArticleDOI
TL;DR: Not only the phase composition with high cubic phase content but also the lattice parameters and the yttria content in the remaining t-ZrO2 played a determinant role for PSZs to be used as 'high-translucent' zirconia.

Journal ArticleDOI
TL;DR: The corrosion resistance and mechanical properties of CoCrFeNiTi0.5 alloy are much better than the other three groups, which promotes the development of HEA systems with high value for industrial application.
Abstract: In this paper, CoCrFeNiTix high entropy alloy (HEA) coatings were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and corrosion resistance of the coatings were studied. The mechanism of their corrosion resistance was elucidated experimentally and by first-principles calculations. The results show that CoCrFeNiTi0.1 adopts a face-centered cubic (FCC) phase, CoCrFeNiTi0.3 exhibits an FCC phase and a tetragonal FeCr phase, and CoCrFeNiTi0.5 adopts an FCC phase, a tetragonal FeCr phase, and a rhombohedral NiTi phase. The FCC phase, tetragonal FeCr phase, rhombohedral NiTi phase, and hexagonal CoTi phase are all observed in the CoCrFeNiTi0.7 HEA. The alloys assume the dendritic structure that is typical of HEAs. Ni and Ti are enriched in the interdendritic regions, whereas Cr and Fe are enriched in the dendrites. With increasing Ti content, the hardness of the cladding layers also increases due to the combined effects of lattice distortion and dispersion strengthening. When exposed to a 3.5 wt.% NaCl solution, pitting corrosion is the main form of corrosion on the CoCrFeNiTix HEA surfaces. The corrosion current densities of CoCrFeNiTix HEAs are much lower than those of other HEAs. As the Ti content increases, the corrosion resistance is improved. Through X-ray photoelectron spectroscopy (XPS) and first-principles calculations, the origin of the higher corrosion resistance of the coatings is connected to the presence of a dense passivation film. In summary, the corrosion resistance and mechanical properties of CoCrFeNiTi0.5 alloy are much better than the other three groups, which promotes the development of HEA systems with high value for industrial application.

Journal ArticleDOI
TL;DR: In this article, the first extensive crystal structures search of W-Si system over a wide range of stoichiometries at ambient condition, using first-principles swarm intelligence structure search methods, is presented.

Journal ArticleDOI
TL;DR: In this paper, a multiphase dendritic microstructure with W-rich dendrites and V2.5Cr1.2WMoCo0.04 was fabricated by arc melting and was found to exhibit a multi-phase XRD pattern, which attests to the BCC crystal structure observed in the as-cast state being metastable.

Journal ArticleDOI
TL;DR: In this paper, single crystal and textured polycrystalline γ-Al2O3 thin films were synthesized by oxidation of NiAl(110) in air at 850 °C for 1 and 2 hours, respectively, by comparison of selected-area electron diffraction (SAED).

Journal ArticleDOI
Junming Gou1, Tianzi Yang1, Ruihua Qiao1, Yao Liu1, Tianyu Ma1 
TL;DR: In this article, the formation mechanism of tetragonal nanoprecipitates that may dominate the large magnetostriction of Fe-Ga alloys remains unclear, but it is shown that both L60-and D022-type face-centered-tetragonal (SCT) nanoprecipient are precursors of the facecentered-cubic L12 equilibrium phase, as identified in the isothermally aged Fe73Ga27 and Fe74Ga26 alloys, respectively.

Journal ArticleDOI
TL;DR: In this article, the authors used pyrolysis to synthesize polycrystalline ZnGa2S4 thin films of different thicknesses for X-ray diffraction.

Journal ArticleDOI
TL;DR: In this paper, the influence of support crystalline phase structure on the dispersion behaviors of the supported metal oxides, tetragonal rutile RuO2 supported on both tetrangular anatase a-TiO2 and tetragonal rutiles r-Ti O2 supports with different loadings have been investigated, and it has been discovered that the monolayer dispersion capacity of RuO 2 on r- TiO2 support is 0.84 mmol per 100 m2 surface, which is much higher than 0.15 mmol per 100 mm2

Journal ArticleDOI
TL;DR: In this article, the effects of doping, vacancy creation, anisotropic broadening, and preferred orientation on the intensity of X-ray diffraction (XRD) peaks were analyzed using tetragonal bismuth oxyhalides as examples.
Abstract: Crystals with exposed facets are popular materials in many catalytic applications due to their high reactivity. Facet identification is often conducted by transmission electron microscopy (TEM). In this work, we analyze the effects of doping, vacancy creation, anisotropic broadening, and preferred orientation on the intensity of X-ray diffraction (XRD) peaks by using tetragonal bismuth oxyhalides (BiOX, X = Cl, Br, and I) as examples. The differences in these effects were successfully used to identify the preferentially exposed (001) facets of BiOX nanoplates synthesized by a polymer-assisted precipitation method. In comparison to TEM, the XRD analysis is not only cheaper and easier to perform, but also it gives results representative for the sample. This work aims to provide further justification for the use of XRD as a powerful and handy characterization technique in the field of crystal facet engineering.

Journal ArticleDOI
TL;DR: The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential two-dimensional derivatives.
Abstract: All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal Ti2InB2. Inspired by the recent discovery of chemically ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore chemical ordering upon metal alloying of M2AlB2 (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane chemical ordering are identified, coined i-MAB, along with 16 disordered stable alloys. The predictions are verified through the powder synthesis of Mo4/3Y2/3AlB2 and Mo4/3Sc2/3AlB2 of space group R3m (no. 166), displaying the characteristic in-plane chemical order of Mo and Y/Sc and Kagome ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential two-dimensional derivatives.

Journal ArticleDOI
TL;DR: In this article, the authors show that topological phonons (nodal rings, nodal lines, and Weyl points) are ubiquitous in oxide perovskites in terms of structures (tetragonal, orthorhombic, and rhombohedral) and external conditions (photoexcitation, strain, and temperature).
Abstract: Perovskite oxides exhibit a rich variety of structural phases hosting different physical phenomena that generate multiple technological applications. We find that topological phonons—nodal rings, nodal lines, and Weyl points—are ubiquitous in oxide perovskites in terms of structures (tetragonal, orthorhombic, and rhombohedral), compounds (BaTiO3, PbTiO3, and SrTiO3), and external conditions (photoexcitation, strain, and temperature). In particular, in the tetragonal phase of these compounds, all types of topological phonons can simultaneously emerge when stabilized by photoexcitation, whereas the tetragonal phase stabilized by thermal fluctuations only hosts a more limited set of topological phonon states. In addition, we find that the photoexcited carrier concentration can be used to tune the topological phonon states and induce topological transitions even without associated structural phase changes. Overall, we propose oxide perovskites as a versatile platform in which to study topological phonons and their manipulation with light.

Journal ArticleDOI
TL;DR: The main results indicate a good agreement between XRD and optical analysis, therefore demonstrating that the structural transition from monoclinic to tetragonal phases is the dominating mechanism for controlling the global properties of the SMT transition.
Abstract: A detailed structural investigation of the semiconductor-to-metal transition (SMT) in vanadium dioxide thin films deposited on sapphire substrates by pulsed laser deposition was performed by in situ temperature-dependent X-ray diffraction (XRD) measurements. The structural results are correlated with those of infrared radiometry measurements in the SWIR (2.5-5 μm) and LWIR (8-10.6 μm) spectral ranges. The main results indicate a good agreement between XRD and optical analysis, therefore demonstrating that the structural transition from monoclinic to tetragonal phases is the dominating mechanism for controlling the global properties of the SMT transition. The picture that emerges is a SMT transition in which the two phases (monoclinic and tetragonal) coexist during the transition. Finally, the thermal hysteresis, measured for thin films with different thickness, showed a clear dependence of the transition temperature and the width of the hysteresis loop on the film thickness and on the size of the crystallites.

Journal ArticleDOI
TL;DR: In this article, a 0.5mm CsPbCl3 perovskite single crystal with tetragonal structure and a direct band gap of 2.86 ± 0.3
Abstract: Inorganic perovskite has attracted great interest due to its excellent optoelectronic properties. There are much less low band gap halide perovskite semiconductors, and CsPbCl3 is one of a wide band gap semiconductor in the perovskite family. In this study, a 0.5-mm CsPbCl3 perovskite single crystal with tetragonal structure and a direct band gap of 2.86 ± 0.3 eV is synthesized by flash evaporation of CsCl-PbCl2 solution. An ultraviolet photodetector based on a CsPbCl3 single crystal is fabricated, showing a photoresponse in a wide wavelength range of 280–435 nm, with a maximum responsivity of 0.272 A/W at 410 nm. Rise and decay response times of the device are less than 28.4 and 2.7 ms, respectively. The good performance of this CsPbCl3 photodetector indicates promising applications in the field of UV optoelectronic devices.

Journal ArticleDOI
TL;DR: In this paper, the influence of Ni doping on the structural, optical, dielectric, ferroelectric and magnetic properties of nanocrystalline BaTi1-xNixO3 ceramics synthesized by sol-gel auto combustion process is highlighted.

Journal ArticleDOI
TL;DR: In this article, the phase stability and onset crystallization temperature of polymorphic (HfxZr1−x)O2 (HZO) thin films were investigated via high-temperature x-ray diffraction (HTXRD) for five different compositions.
Abstract: Polymorphic (HfxZr1−x)O2 (HZO) thin films exhibit ferroelectric, dielectric, and antiferroelectric properties across a wide compositional range due to the existence of orthorhombic, monoclinic, and tetragonal phases. To better understand the phase stability across the HfO2–ZrO2 compositional range, we investigate the structural evolution of HZO thin films in situ via high-temperature x-ray diffraction (HTXRD) for five different compositions [ZrO2, (Hf0.23Zr0.77)O2, (Hf0.43Zr0.57)O2, (Hf0.67Zr0.33)O2, and HfO2]. The real-time monitoring of HZO crystallization reveals a competing driving force between the tetragonal and monoclinic phase stabilities for HfO2-rich vs ZrO2-rich compositions. Additionally, we confirm an XRD peak shift toward lower 2θ with increasing temperature in ZrO2, (Hf0.23Zr0.77)O2, and (Hf0.43Zr0.57)O2 films, which we ascribe to the appearance of a metastable orthorhombic phase during heating. A monotonic trend for the onset crystallization temperature is reported for five compositions of HZO and reveals an increase in onset crystallization temperature for HfO2-rich compositions. Relative intensity fraction calculations suggest a higher fraction of monoclinic phase with increasing annealing temperature for (Hf0.67Zr0.33)O2. This study of phase stability and onset crystallization temperatures offers insight for managing the thermal budget for HZO thin films, especially for temperature-constrained processing.

Journal ArticleDOI
TL;DR: In this paper, Ba and Sb co-doped SnO2 (BATO2) thin films have been deposited on the glass substrates by cost-effective spray pyrolysis method.

Journal ArticleDOI
TL;DR: In this paper, the X-ray diffraction profile shows that a small amount of La3+-substitution for Ba2+-site is more effective for the enhancement of ferroelectric and piezoelectric properties, similarly to the donor La3-doped Pb(Zr,Ti)O3 ceramic.

Journal ArticleDOI
Ming Ma1, Song Xia1, Kexin Song1, Haisheng Guo1, Shiji Fan1, Zhenrong Li1 
TL;DR: In this article, temperature dependance of induced dielectric and piezoelectric properties in the [001]-oriented predirect current poling (DCP) of the 0.43PMN-0.32PT single crystals near morphotropic phase boundary was investigated using the alternating current treatment (ACT).
Abstract: In this paper, temperature dependance of induced dielectric and piezoelectric properties in the [001]-oriented predirect current poling (DCP) of the 0.25Pb(In1/2Nb1/2)O3-0.43Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (0.25PIN-0.43PMN-0.32PT) single crystals near morphotropic phase boundary was investigated using the alternating current treatment (ACT). By the optimized ACT conditions of 1 kV/mm at 50 Hz over 20 cycles, the dielectric permittivity (ɛ33T/ɛ0) and piezoelectric coefficient (d33) at room temperature of the DCP-ACT crystal were improved to be 7120 and 2610 pC/N, which were 48% and 54% higher than that of the DCP crystal (ɛ33T/ɛ0 = 4800, d33 = 1700 pC/N). Based on the temperature dependence of dielectric permittivity and dielectric loss of the DCP-ACT crystal, the induced monoclinic phases (MA and MC) were involved in the phase transition process from a rhombohedral phase to a tetragonal phase. The phase transition temperatures TR-MA of 116 °C of the DCP-ACT crystal showed about 10 °C higher than that of DCP. Meanwhile, ɛ33T/ɛ0 of the DCP-ACT crystal at TR-MA and in the tetragonal phase region, at around 110 °C and 130 °C, were 160% and 390% higher than those of the DCP crystal, respectively. The ultrahigh ɛ33T/ɛ0 = 17 000 of the DCP-ACT crystal at 130 °C may relate to the nanoscale heterogeneous polar-regions induced by ACT. The ACT is a promising way to enhance the dielectric and piezoelectric performance of the pre-DCP 0.25PIN-0.43PMN-0.32PT single crystals with broadened temperature range for device applications.

Journal ArticleDOI
K. Park1, D.A. Hakeem1, D.H. Kim1, G.W. Jung1, S.W. Kim 
TL;DR: Li7La3Zr2O12 oxides satisfied the criteria, proposed by F. C. Hawthorne, for the formation of garnet structure as discussed by the authors, and showed that the as-synthesized and aged phosphors formed a tetragonal crystal structure and emitted efficient red light.