Tetragonal Crystals Research Articles

Preparation and antibacterial evaluation of silver-doped zirconia for enhanced dental restoration performance

Because of its superior strength, esthetic properties, and excellent biocompatibility, zirconia is preferred for dental prosthetic such as crowns and bridges. However, zirconia crowns and bridges are susceptible to secondary caries owing to margin leakage. Silver is a well-known antibacterial agent, making it a desirable additive to zirconia crowns and bridges for secondary caries prevention. This study focuses on imparting zirconia composite with antibacterial properties to enhance its protective capacity in dental restorations. We used the sol-gel method to dope Ag into zirconia. Silver-doped zirconia powders were prepared at Zr:Ag molar ratios of 100:0,100:0.1, 100:0.5, 100:1, 100:3, and 100:5 (respective samples denoted as Ag-0, Ag-0.1, Ag-0.5, Ag-1, Ag-3, and Ag-5) and were subjected to firing at various temperatures (400 °C-1000 °C). We performed x-ray diffraction to investigate the crystal phase of these powders and x-ray fluorescence and field emission scanning electron microscopy to analyze their elemental composition and surface morphology, respectively. Moreover, we performed spectrophotometry to determine theL*a*b* color values, conducted dissolution tests, and quantified the Ag content through inductively coupled plasma optical emission spectroscopy. In addition, we studied the antibacterial activity of the samples. Analyses of the samples fired at ⩽600 °C revealed a predominantly white to grayish-white coloration and a tetragonal crystal phase. Firing at ⩾700 °C resulted in gray or dark gray coloration and a monoclinic crystal phase. The Ag content decreased after firing at 900 °C or 1000 °C. Ag-0.5 and above exhibited antibacterial activity against bothEscherichia coliandStaphylococcus aureus. Therefore, the minimum effective silver-doped zirconia sample was found to be Ag-0.5. This study allows the exploration of the antimicrobial potential of silver-doped zirconia materials in dental applications such as prosthdontical lining materials, promoting the development of innovative restorations with protective capacity against secondary caries.

High second-order nonlinearity in single-domain tetragonal PMN-PT single crystal

Recently, Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystals present tremendous potential in optical applications such as Q-switches and invisible robotic devices because they possess high electro-optic properties and perfect transparency simultaneously. However, due to the difficulties in testing and sample preparation, the nonlinear optical properties of PMN-PT single crystals have not been reported yet, which poses a bottleneck for exploring its nonlinear application. In this work, a large second-order nonlinear coefficient (d31 ∼ 77.9 pm V−1) of single domain PMN-0.39PT single crystal has been revealed, which is times times higher than the maximum nonlinear coefficient of commercial LiNbO3 single crystal (d33 = 25.4 pm V−1). The complete set of nonlinear coefficients of the sample has been determined by second harmonic generation microscopy. This work presents the promising nonlinear optical property in PMN-PT single crystals and opens a door for designing high-performance nonlinear optical devices.

Immobilization of simulated An4+ in radioactive sludge via microwave sintering: Mechanistic and performance

In this study, we investigate radioactive sludge containing An4+ ions via simulation. Ce4+ is employed as a surrogate isotope for An4+ ions, and silicate glass particles are incorporated as stabilizing agents. Continuous microwave sintering technology is adopted to sinter the simulated radioactive sludge with varying CeO2 contents co-doped with 60 wt.% glass particles at temperatures of 1100 °C, 1200 °C, and 1300 °C to achieve sample vitrification. The phase evolution, microstructure, morphology, chemical stability, sample density, and porosity of the sintered specimens are analyzed comprehensively. The results indicate distinct maximum solubility limits at different sintering temperatures: 5 wt.%, 6 wt.%, and 13 wt.% for 1100 °C, 1200 °C, and 1300 °C respectively. Under these conditions, Ce is immobilized within the glass network structure. Notably, the Ce3+/Ce4+ ratio in the 1300 °C-Ce10 specimen reaches 2.04, and the combined percentage of Q3 and Q4 glass structural units exceeds 50 %. Beyond the optimal solubility limit, tetragonal CeO2 crystals are formed on the glass sample surface. The normalized leaching rate of Ce from the samples remains at 5.0 × 10−6 g m−2 d−1. Additionally, the sintered samples indicate densities ranging from 2.65 to 3.01 g/cm3 and porosities from 0.18 % to 1.8 %. This study introduces a novel perspective for addressing radioactive sludge treatment.

Electromechanical properties and domain evolution of a tetragonal Er3+-doped Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric single crystal

Herein, a tetragonal Er3+-doped Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystal is comprehensively investigated. The actual composition of the studied crystal is Pb(Mg1/3Nb2/3)O3–36PbTiO3 doped with 0.17-mol% Er3+ (PMN–36PT: 0.17-mol% Er3+). The crystal exhibits a high shear piezoelectric constant of ∼936 pC/N, approximately three times the longitudinal piezoelectric constant when poled along [001]c, as well as a higher Curie temperature of ∼170 °C and large coercive field of ∼4.58 kV/cm. At room temperature, the crystal presents a mass of domain walls along the <110>c direction and extinction is observed four times within a 360° rotation, showing typical domain features of the tetragonal phase. Under a direct current–electric field along the [010]c direction, the extinction rule remains unchanged; however, changes in the domain configuration can be observed. In addition, the orientation dependence of the piezoelectric constant, dielectric coefficient, elastic compliance constant, and electromechanical coupling factor is calculated using the coordinate transformation method. The findings of this study are of considerable importance for the fundamental studies and device design of tetragonal ferroelectric crystals.

Formation of self-assembled nanodomain structure as a result of motion of oriented planar phase boundary in single crystals of tetragonal PMN-PT

We studied the formation of the domain structure as a result of the motion of a planar interphase boundary in the {001}-cut tetragonal PMN-PT crystals during cooling with oriented temperature gradient. The specialized heating/cooling stage was assembled for this purpose. Piezoresponse force microscopy was used to image the domain structure at the (001) and (010) surfaces of the samples with high spatial resolution, revealing a complex quasi-periodic domain pattern with a periodicity from 300 to 400 nm.

Comparison of the structure and physicochemical properties of ZrO2 based crystals partially stabilized with Y2O3, Gd2O3 and Sm2O3

The phase composition, density, microhardness and fracture toughness of (ZrO2)1-x(R2O3)х crystals (where R = Y, Sm and Gd) for x = 0.02–0.04 have been compared. The crystals have been grown using directional melt crystallization in a cold crucible. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The microhardness and fracture toughness of the crystals have been evaluated by means of indentation. At stabilizing oxide concentrations of ≥ 2.8 mol.% for Y2O3 and Gd2O3 and ≥ 3.7 mol.% for Sm2O3 the crystals have densities close to the theoretical ones and contain two tetragonal phases. At lower stabilizing oxide concentrations the crystals contain the monoclinic phase. The fracture toughness of the tetragonal crystals increases with the ionic radius of the stabilizer. The highest fracture toughness values achieved when stabilized by a specific oxide are 11.0, 13.0 and 14.3 MPa·m1/2 for the 2.8YSZ, 2.8GdSZ and 3.7SmSZ crystals, respectively. The fracture toughness proves to depend on the crystallographic orientation of the crystals. The results of this work can be used in the design and fabrication of various structural components and devices.

Endowing Ferroelectric Properties of Tetragonal Lysozyme Crystals through C60 Doping

The inherent nonpolarity of tetragonal lysozyme crystals excludes a ferroelectricity response. Herein, we present a demonstration of achieving measurable ferroelectricity in tetragonal lysozyme crystals through C60 doping. Ferroelectric characterizations revealed that C60-doped tetragonal lysozyme crystals exhibited typical characteristic ferroelectric hysteresis loops. Crystallographic structural analysis suggested that C60 doping may induce a reduction in the overall symmetry of tetragonal Lys@C60, leading to the observed ferroelectricity response. Moreover, the introduction of C60 facilitates efficient electron transport inside the crystal and influences the polarization of Lys@C60, further contributing to the observed ferroelectricity response. This work verifies that C60 doping can serve as a simple strategy to bestow novel ferroelectric properties to non-ferroelectric lysozyme crystals, potentially rendering them suitable for biocompatible and biodegradable application in implantable and wearable bioelectronics.

Preparation of Eu2+ and Dy3+ co-doped Sr2MgSi2O7 translucent long afterglow glass-ceramics by recrystallization-melting and their luminescence properties

In this work, a novel recrystallization-melting method was used to prepare Eu2+ and Dy3+ co-doped Sr2MgSi2O7 translucency long afterglow glass-ceramics with complete crystal development. The synthesis mechanism is discussed by analyzing the detection results of X-ray diffraction, scanning electron microscopy, phosphorescence spectra, and afterglow attenuation curves. The effect of different firing temperatures and crystallization time on the crystalline phase content, crystal size, and luminescence properties of the Sr2MgSi2O7:Eu2+, Dy3+ glass-ceramics samples were examined. The results show that, as compared with the traditional melt crystallization method or the two-step method, the recrystallization–melting method is able to form some Sr2MgSi2O7:Eu2+, Dy3+ crystals first under a temperature that is lower than that of the glass transition. With increasing firing temperature and crystallization time, crystal growth and recrystallization reached an equilibrium state, accompanied by the generation of liquid glassy phases. It is found that the afterglow properties are proportional to the crystalline phase content and crystal size, with the latter having a more significant effect. Under the condition of firing at 1050 °C for 10 h, tetragonal Sr2MgSi2O7 crystals with a maximum size of 20 μm were successfully synthesized for the first time. These crystals exhibited high integrity and optimal afterglow performance, with a duration close to 2 h. The recrystallization-melting method suits industrial production on large scales, and the firing temperature is evidently lowered, which effectively reduces the energy consumption of the synthesis process and significantly improves the long afterglow performance.

Comprehensive DFT investigation of ternary thallium tetragonal crystals: assessing their viability for solar cell applications

To ascertain the suitability of the TlInX2 (X = S, Se, Te) tetragonal structures for photovoltaic applications, first-principles calculations were carried out using the pseudopotential plane wave method to assess the structural, electronic, elastic, and optical characteristics of the considered compounds via the DFT software CASTEP. For all three compounds, our calculated structural parameters were in excellent agreement with both the experimental and previous theoretical results. Our calculations provided the first predicted elastic constants for the TlInS2, TlInSe2 and TlInTe2 compounds. The three tetragonal systems were mechanically stable and exhibited pronounced and noticeable elastic anisotropy. Analysis of the optical properties revealed that TlInX2 (X = S, Se, Te) exhibited distinct absorption in the ultraviolet radiation range and pronounced optical anisotropy. The calculated bandgap values obtained using the HSE06 hybrid functional were 1.68 eV, 1.38 eV, and 1.36 eV for TlInS2, TlInSe2 and TlInTe2, respectively. These findings are of significant interest because they categorize all three compounds as promising candidates for use in photovoltaic cell applications.

Synthesis and Characterization of Lithium-doped BaTiO3/Si(100) Thin Films with Variations of 0 %, 0.5 %, 1 % and 1.5 % as Potential Forerunners of Solar Cells

Thin films of BaTiO3/Si(100) in Lithium with doping variations of 0%, 0.5%, 1%, and 1.5% were successfully grown on a p-type Si substrate using Chemical Solution Deposition method. The films were annealed at 850 °C for 15 hours. The crystal structure was characterized using X-Ray Diffraction (XRD) with Material Analysis Using Diffraction (MAUD), Scanning Electron Microscope- Energy Dispersive X-Ray (SEM-EDX), optical absorption, and current – voltage (I-V) as potential solar cells. The results showed that the addition of Lithium doping affected the value of the lattice parameters and formed tetragonal crystals. The characterization results show that the bandgap energy value of the thin film due to lithium doping reduces the bandgap energy value because the donor atom added to a semiconductor causes the allowable energy level to be slightly below the conduction band. The presence of this new band causes the thin film bandgap energy to decrease with a five-valent tantalum dip. The morphological properties showed that the BaTiO3/Si(100) thin film particles in the deposited Lithium had a reasonably homogeneous grain. With the addition of lithium acetate as a binder into barium titanate, the grain size is getting smaller because it is suspected that the lithium-ion radius is smaller than the barium-ion radius. Measurement of I-V on the thin film shows that the output voltage value increases with more light intensity hitting the surface of the thin film. The greater the light intensity, the greater the energy of the photons, so the electrons are easier to jump. The three things above (both electrical and morphological properties) conclude that the thin films grown have the potential for solar cells.

Structural and resistivity properties of Fe1-xCoxSe single crystals grown by the molten salt method

A series of tetragonal Fe1-xCoxSe single crystals with a complete Co doping range (0 ≤ x ≤ 0.52) up to its solid solubility limit in FeSe have been grown by an eutectic AlCl3/KCl molten salt method. The typical lateral size of as-grown Fe1-xCoxSe single crystals is 1–5 mm. The chemical composition and homogeneity of the crystals was examined by both inductively coupled plasma atomic emission spectroscopy and energy dispersive spectrometer. X-ray diffraction analysis demonstrates that the crystal lattice parameters a and c are both linearly decreased with increasing Co doping level x. In the whole doping range, all the samples show metallic behaviour in contrast to a metal insulator transition of Cu-doped FeSe according to the resistivity measurements.

Polyamide Electrospun Nanofibers Functionalized with Silica and Titanium Dioxide Nanoparticles for Efficient Dye Removal

In this work, novel multifunctional electrospun nanofibrous membranes made of polyamide (PA6) and loaded with silica (SiO2) and/or titanium dioxide (TiO2) nanoparticles were fabricated. SiO2 NPs were first prepared and then characterized by TEM, FE-SEM, and FTIR, and by using XRD techniques, confirming the formation of cristobalite tetragonal crystals with high purity. Different nanofibrous mats, loaded with SiO2 NPs, TiO2 NPs, or both SiO2 and TiO2 NPs, were investigated. Morphological studies indicated that SiO2 and TiO2 nanoparticles tend to be arranged along the fiber surface, also promoting the formation of anatase nanorods when they are mixed into the nanofibers. In this last scenario, mechanical tests have demonstrated that the presence of SiO2 contributed to balancing the mechanical response of fibers that are negatively affected by the presence of TiO2 NPs—as confirmed by tensile tests. More interestingly, the presence of SiO2 did not negatively affect the antibacterial response against different bacteria populations (i.e., Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, Bacillus subtilis, and Candida albicans), which is mainly ascribable to the presence of TiO2 particles. Accordingly, the TiO2- and TiO2/SiO2-loaded fibers showed higher methylene blue (MB) absorption values—i.e., 26 mg/g and 27 mg/g—respectively, compared to the SiO2-loaded fibers (23 mg/g), with kinetics in good agreement with the second-order kinetic model. The obtained findings pave the way for the formation of novel antibacterial membranes with a promising use in water purification.

Growth, spectroscopy and SESAM mode-locking of a "mixed" Yb:Ca(Gd,Y)AlO4 disordered crystal.

We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb3+:Ca(Gd,Y)AlO4. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO4 crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347 mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90 nm (1010 - 1100 nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8 nm with an average output power of 51 mW at ∼65.95 MHz. The average output power can be scaled to 105 mW for slightly longer pulses of 42 fs at 1063.5 nm.

Tetragonal phase-free crystallization of highly conductive nanoscale cubic garnet (Li6.1Al0.3La3Zr2O12) for all-solid-state lithium-metal batteries

The synthesis and processing of garnet-type conductors is usually done at temperatures above 1100 °C to reach the high Li-ion conducting cubic phase resulting in micron-sized particles and potential Li-loss, which are unfavorable for further processing and electrode-electrolyte assembly. Here, we tackle this problem and report a novel low-temperature aqueous synthesis route to stabilize the cubic phase of Li6.1Al0.3La3Zr2O12 (c-Al-LLZO) at a temperature as low as 600 °C, while obtaining nano-crystallites at around 100 - 200 nm. Moreover, a dual-reaction mechanism was proposed to describe the process of c-Al-LLZO crystallization. The as-synthesized nanoscale c-Al-LLZO particles facilitate the densification of the solid-state electrolyte (SSE) pellets with less endowed grain boundaries (exhibiting a high relative density of 97.8 %). The ionic conductivity reaches 0.42 mS cm−1 at 21 °C and the low activation energy (half of the published values) is 0.17 eV. The results presented here show that symmetric cells with Li metal exhibit excellent stability at the current density of 0.2 mA/cm2 and 0.5 mA/cm2, and an improved critical current density (CCD) of 2.16 mA/cm2. This work provides a feasible method of low-temperature crystallization of nanoscale cubic garnet SSEs with good performance for the fabrication of stable SSLBs.

Domain engineering in ferromagnetic morphotropic phase boundary with enhanced and non-hysteretic magnetostriction: A phase-field simulation

Giant and non-hysteretic magnetostriction is critical for magneto-mechanical applications, such as transducers, sensors, and actuators. In this work, the introduction of domain engineering into the single crystals near the ferromagnetic morphotropic phase boundary (MPB) is achieved through phase-field simulation, with the aim of exerting control over domain configuration and magnetostriction. It is found that intermediate external magnetic fields applied along non-easy magnetic axes during the nucleation stage can significantly affect the subsequent domain growth and evolution kinetics. The simulations reveal a domain wall broadening mechanism to explain the significantly improved non-hysteretic magnetoelastic responses observed in engineered tetragonal crystals. Our simulation results additionally demonstrate a discernible correlation between the domain wall densities and external fields in the engineered tetragonal domain. This research provides a potential pathway for the advancement of giant and non-hysteretic magnetostrictive material designs.

Phosphorus removal from water using La-based absorbents: Insights into the impacts of crystal structure, surface area, and crystallinity on the removal efficiency and mechanisms

Removal of nutrients and pollutants from water using structured adsorbents is of great interest. Lanthanum (La) oxide/hydroxides and their derivative composites are promising platforms for phosphate (P) removal from wastewater. However, various key factors including crystal structure, specific surface area (SBET) and crystallinity restrict their P removal performance. In this study, LaOCl, a novel adsorbent with tetragonal crystal, and La2O3, a traditional adsorbent with hexagonal crystal, were prepared at different calcination temperatures and tested as P adsorbents. Due to different crystal structures, LaOCl and La2O3 exhibit significant differences in P adsorption. LaOCl crystal is more stable than La2O3 in solution. The main LaOCl crystal phase is not changed after P adsorption, while La2O3 transformed into La(OH)3 due to proton capturing form H2O. The Cl− on LaOCl can be used as a ligand for P ions exchange. It is different from OH− exchange which increases the pH sharply. The isoelectric points (IEP) of LaOCl is slightly higher than La2O3. All of these factors, caused by the different structures of LaOCl, keep its P adsorption capacity and rate high in acidic conditions. The Langmuir maximum P adsorption capacity of LaOCl is 164.52 mg/g, which is 2.3 times greater than La2O3. The LaOCl adsorbent exhibited a faster adsorption rate than La2O3. It is able to reduce the H2PO4− concentration from 50 mg/L (pH ∼ 5.0) to < 0.002 mgP/L in 180 min, while the residual P concentration is about 11.27 mgP/g by La2O3 in the same time. The P adsorption capacity was found positively correlated with crystallinity at pH 3.0 but with SBET only in pH 5.0 ∼ 9.0 range for LaOCl. However, SBET and crystallinity are not the main factors influencing the P adsorption capacity of La2O3. Following P adsorption, both adsorbents were verified for P desorption. The results showed the amount of P desorbed was small, thus the adsorbents have the ability to lock P in natural water. Overall, this study provides essential perspectives on the effects of crystal structure, surface area, and crystallinity on P adsorption and the scientific basis for developing new and functionalized La-based adsorbents.

Combination of Tetragonal Crystals with LiTaO3 Thin Plate for Transverse Resonance Suppression of Surface Acoustic Wave Devices.

This paper discusses combination of tetragonal crystals with LiTaO3 (LT) thin plate for complete transverse resonance suppression of surface acoustic wave devices without k2 deterioration by manipulating the slowness shape. Besides, better lateral energy confinement is achieved as well by the use of double busbar structure. First, the mechanism of slowness shape manipulation by combining tetragonal crystals is studied. By comparison, YZ-lithium tetraborate (LBO) shows better performance than 69°Y90°X quartz. Then numerical simulations are carried out using periodic three-dimensional finite method assisted by hierarchical cascading technique, and the effectiveness of transverse mode suppression by flattening the slowness shape is revealed. And the possibility to realize temperature compensation is discussed owing to the unique material property of LBO. Moreover, the capability of other tetragonal crystals for slowness manipulation are compared, and LBO is the best choice among these tetragonal crystals.

Enhanced piezoelectric and optical properties of tetragonal Sm‐doped Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 crystals

AbstractRelaxor ferroelectric single crystal Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) has received extensive research and attention due to its excellent piezoelectric, electromechanical, and other properties. In particular, tetragonal relaxor ferroelectric single crystals have shown greater application potential in high‐temperature devices due to their higher Curie temperature and better stability. However, the low piezoelectric performance of tetragonal crystals also greatly limits its application, and research on its optical properties is not sufficient. In this paper, the tetragonal phase Sm–PIN–PMN–PT single crystal was obtained by the Bridgman method, and its piezoelectric and electro‐optical properties are studied. At the same time, we gave a complete set of piezoelectric, dielectric, and elastic coefficient matrices. The results show that the crystal has excellent piezoelectric and electromechanical properties. The piezoelectric coefficient can reach 905pC/N, the electromechanical coupling coefficient k33 is 85%, and the kt is 72%. The transmittance of the sample polarized along [001] direction can reach 66%. The effective electro‐optical coefficient γc is 60 pm/V at room temperature and can reach 86 pm/V at 70°C. It has a wide operating temperature range and stable performance with frequency variation, which has certain reference significance for application in new electro‐optical devices.

High pressure freezing and cryo-sectioning can be used for protein structure determination by electron diffraction

Electron diffraction of three-dimensional nanometer sized crystals has emerged since 2013 as an efficient technique to solve the structure of both small organic molecules and model proteins. However, the major bottleneck of the technique when applied to protein samples is to produce nano-crystals that do not exceed 200 to 300 nm in at least one dimension and to deposit them on a grid while keeping the minimum amount of solvent around them. Since the presence of amorphous solvent around the crystal, necessary to preserve its integrity, increases the amount of diffuse scattering, thus degrading the signal-to noise ratio of the diffraction signal, other sample preparation strategies have been developed. One of them is the milling of thin crystal lamella using focused ion beam (FIB), which was successfully applied to several protein crystals. Here, we present a new approach that uses cryo-sectioning after high pressure freezing of dextran embedded protein crystals. 150 to 200 nm thick cryo-sections of hen egg white lysozyme tetragonal crystals where used for electron diffraction experiments. Complete diffraction data up to 2.9 Å resolution have been collected and the lysozyme structure has been solved by molecular replacement and refined against these data. Our data demonstrate that cryo-sectioning can preserve protein structure at high resolution and can be used as a new sample preparation technique for 3D electron diffraction experiments of protein crystals. The different orientations found in the crystal chips and their large number resulting from the cryo-sectioning make the latter an attractive approach as it combines advantages from both blotting approaches (number of crystals) and FIB-milling (controlled thickness and absence of solvent around the crystal).

Paired charge-2 Weyl-Dirac phonons in tetragonal crystals

Paired charge-2 Weyl-Dirac phonons in tetragonal crystals