Search Results (28)

We report the growth of YTiO₃ single crystals using different starting materials with the nominal compositions, (1) stoichiometric YTiO₃; (2) oxygen deficient YTiO_2.925; (3) oxygen deficient YTiO_2.85, and different atmospheres, (1) 97%Ar/3%H₂; (2) Ar; (3) forming gas 95%N₂/5%H₂, using the laser floating zone growth technique. The oxygen-deficient starting materials were prepared by mixing Y₂O₃, Ti₂O₃, and Ti powder according to the YTiO_3-δ stoichiometry. The addition of Ti powder to the starting materials effectively reacts with the oxygen in the floating zone furnace chamber, reducing Ti⁴⁺ ion-containing impurities. High-quality YTiO₃ single crystals with (2 0 0) facet were grown from the starting materials corresponding to the nominal composition YTiO_2.925. YTiO₃ single crystals grown from different starting materials are characteristic of oxygen content of 3 in both pure crystals and crystals containing impurities, revealed by the same oxygen occupancy in single crystal X-ray diffraction measurements. When forming gas was used, a golden TiN coating formed on the surface of rod. Full article

This review describes the recent progress of floating-zone techniques for bulk single-crystal growth. The most crucial point of the crucible-free technique is to keep the molten zone stable. It has been investigated and reported to yield a steeper temperature gradient at the liquid–solid interface along the growth direction and a homogeneous molten liquid along the rotation axis. This article overviews several recent achievements starting from the conventional setup, particularly for lamps equipped in horizontal or vertical configurations, tilting mirrors, shielding the irradiation, and filament sizes for the optical-lamp floating-zone furnaces. Also, the recently advancing laser-heated floating-zone furnaces are described. Throughout the article, the author emphasizes that the floating-zone technique has been a powerful tool for crystal growth since the 1950s with its roots in the zone-melting method, and it has still been advancing for further materials’ growth such as quantum materials with modern scientific concepts. Full article

This work proposes the synthesis of strontium ferrite by two different methods: sol-gel (SG), using powdered coconut water (PCW) as a precursor, and laser floating zone (LFZ). The SG samples were after treated at temperatures of 700, 1000, and 1200 °C, while the samples obtained by LFZ were grown at pulling rates of 10, 50, and 100 mm/h. All samples studied were subjected to structural characterization techniques, as well as electrical (AC and DC) and magnetic characterization. Through X-ray diffraction, it was possible to observe that all the samples presented strontium ferrites, but none were single phase. The phases detected in XRD were confirmed by Raman spectroscopy. Scanning electron micrography allowed the observation of an increase in grain size with the temperature of SG samples and the reduction of the porosity with the decrease in growth rate for LFZ fibers. Through electrical analysis, it was observed that the most suitable samples for energy storage were the samples grown at 100 mm/h (${\epsilon }_r^{\prime }$ = 430,712; ${\epsilon }_r^{″}$ = 11,577; tan $\delta$ = 0.84; σ_ac = 0.0006 S/m, at 1 kHz). The remaining samples had high dielectric losses and can be applied in electromagnetic shielding. The SG 700 °C sample presented the highest magnetization (38.5 emu/g at T = 5 K). Full article

In recent years, rare earth silicate compounds have attracted the extensive attention of researchers owing to their potential for applications in scintillation crystals in gamma ray or X-ray detectors, as well as in thermal or environmental barrier coatings. Large high quality crystals of three members of the rare earth monosilicates family of compounds, $R_2{\mathrm{SiO}}_5$ (with R = Dy, Ho, and Er), have been grown by the floating zone method, using a laser-diode-heated floating zone furnace. Crystal growths attempts were carried out using different parameters in order to determine the optimum conditions for the growth of these materials. The phase purity and the crystalline quality of the crystal boules were analysed using powder and Laue X-ray diffraction. Single crystal X-ray diffraction experiments were carried out to determine the crystal structures of the boules. The optimum conditions used for the crystal growth of $R_2{\mathrm{SiO}}_5$ materials are reported. The phase purity and high crystalline quality of the crystals produced makes them ideal for detailed investigations of the intrinsic physical and chemical properties of these materials. Full article

In this work, we have developed and characterized a ceramic composite based on a core of directionally solidified calcium zirconate-calcium stabilized zirconia (CZO-CSZ) eutectic composite coated with a bioactive glass-ceramic. The aim is to research new orthopedic implants as an alternative to conventional 3Y-TZP bioinert ceramics. The CZO-CSZ eutectic rods were grown from the melt of rods of CaO-ZrO₂ in the eutectic composition using the laser floating zone technique (LFZ). The mechanical results indicated that directional eutectics prepared with this technique exhibited good mechanical strength and significant hardness and toughness. The LFZ technique was also used to melt the bioactive coating previously placed by dip coating on the CZO-CSZ rod surface. Depending on the thickness of the coating and the applied laser power, an alloying or coating process was achieved. In the first case, the coating was diluted with the surface of the eutectic cylinder, leading to the segregation of the calcium zirconate and zirconia phases and the formation of a bioactive phase embedding zirconia particles. In the second case, a layer of ceramic glass was formed, well attached to the eutectic cylinder. These layers were both studied from the microstructural and bioactivity points of view. Full article

This study uses a flow visualization method to analyze the flow field of a shed-type coal storage shed, comparing and verifying the findings through numerical calculation. Initially, a coal warehouse-scale model is created for flow visualization. Laser-based cross-sectional analysis yields essential flow data, from which red–green–blue values are extracted, and the flow object with the highest G value is selected. Subsequently, as the video frame changes, the moving object is tracked, and the direction is derived. The velocity vector of the moving object within the designated area is derived. Finally, we compare the results of the flow visualization experiment with the simulation outcome. Notably, the error rate in regions characterized by high flow velocity is found to be low, and a high implementation rate is observed in areas with many floating objects to track. Conversely, implementation accuracy is lower in low-velocity fields. Both methods result in a recirculation zone at the top of the inlet, and a flow stagnation region occurs on the upper part of the central wall. Full article

Triangular lattice magnets have attracted extensive research interest because they are potential hosts for geometrically frustrated magnetism and strong quantum fluctuations. Here, utilizing a laser floating zone technique, we report the first-time successful growth of a DyInO₃ sizable crystal, which contains Dy³⁺-based triangular layers. The fine-tuning of Indium stoichiometry was found to be the key factor in the stabilization of the desired hexagonal phase. The X-ray diffraction study of the crystal structure reveals a non-centrosymmetric P6₃mc space group. Switchable polarization, i.e., ferroelectricity, and ferroelectric domain configuration are experimentally demonstrated at room temperature. Anisotropic magnetic and thermodynamic measurements unveil antiferromagnetic interactions, the absence of long-range ordering down to 0.1 K, and a possible doublet ground state, indicating a strongly frustrated magnetism. Our findings suggest that the DyInO₃ crystal is an excellent platform for studying emergent phenomena and their interplay with coherent topological defects in the quantum realm. Full article

BiFeO₃ fibers were prepared by the Laser Floating Zone (LFZ) technique using different growth speeds. The structural characterization of the samples was undertaken using X-ray diffraction (XRD) and Raman spectroscopy, the morphological characterization by scanning electron microscopy (SEM), and the electrical characterization by impedance spectroscopy. The XRD patterns showed that BiFeO₃ was the major phase in all the samples. Fibers grown at 10 mm/h showed more promising structural and morphological properties. The dielectric characterization revealed that all samples have at least one dielectric relaxation phenomenon that is thermally activated. It was also verified that the dielectric constant is higher at a growth pull rate speed of 10 mm/h. Full article

The successful growth of single crystals of a cubic Laves-phase material HoAl₂ with the space group Fd-3m is reported in this study. The crystals were grown by a floating-zone method with five laser diodes as a heat source. Al-rich feed rods were prepared as compensation for heavy evaporation during the growth. The nominal ratio for the feed rods was optimized as Ho:Al = 1:2.5. Single crystals of HoAl₂ with a length of 50 mm were first grown in this technique. Obtaining the large-sized crystal by the floating-zone method enabled us to systematically explore the physical properties using the same batch crystal. The crystal possessed a second-ordered ferromagnetic transition at 29 K and a first-ordered spin-reorientation transition at 20 K. The bulk physical properties, such as specific heat, magnetic susceptibility, isothermal magnetization, and thermal expansion measurements, were measured. Additionally, a magnetocaloric effect was evaluated by the magnetic entropy change. We demonstrate that anisotropic physical properties along the principal axes ([100], [110], and [111]) emerged below the magnetically ordered states, in contrast to the isotropic behavior in the paramagnetic state. Full article

ZrO₂ is an attractive host matrix for luminescence material because of its excellent physical properties, such as low phonon energy and wide band gap. In this work, the highly transparent Tm₂O₃ and Yb₂O₃ co-doped yttria stabilized zirconia (YSZ) (abbreviated as Yb/Tm: YSZ) single crystals were grown by the optical floating zone method. The Yb/Tm: YSZ samples were stabilized in the cubic phase at room temperature when Yb³⁺ and Tm³⁺ replaced Y³⁺. The influence of Yb³⁺ co-doping on the up-conversion luminescence properties of the crystals was systematically studied. A total of 0.5 mol% Tm₂O₃ and 2.0 mol% Yb₂O₃ co-activated YSZ single crystal (abbreviated as 2.0Yb/Tm: YSZ) has the maximum luminous intensity. There were seven absorption peaks located at around 358, 460, 679, 783.3, 850–1000, 1200, and 1721.5 nm that were observed in the absorption spectrum of the 2.0Yb/Tm: YSZ single crystal. There were three up-conversion peaks at around 488, 658 and 800 nm that were observed when the Yb/Tm: YSZ samples were excitated at 980 nm. The fluorescence lifetime of Tm³⁺ for the ¹G₄→³H₆ transition of the 2.0Yb/Tm: YSZ sample is 7.716 ms as excited with a 980 nm laser. In addition, the oscillator strength parameters Ω_λ (λ = 2, 4 and 6) of this sample were derived by the Judd–Ofelt theory to evaluate the laser performance of the host materials. The ratio Ω₄/Ω₆ of this sample is 0.80, implying its excellent laser output. Therefore, the 2.0Yb/Tm: YSZ single crystal is a considerable potential material for laser and luminescence applications. Full article

The honeycomb TbInO₃ has attracted wide research attention due to its fascinating physical properties. However, TbInO₃ single crystal was difficult to grow owing to the high melting point and serious volatilization of indium during the crystal growth. In this study, the volatilization of the indium element was effectively suppressed by controlling the growth atmosphere and pressure. The excess ratio of indium oxide was determined, and pure hexagonal TbInO₃ crystal was obtained by the laser floating zone method. Systematic studies on the crystal structure and optical and ferroelectric properties were carried out. The structure distortion resulted in the improper geometric ferroelectric revealed by single crystal diffraction and Raman spectrum measurements. The topological vortex domains and P-E hysteresis loop demonstrated the presence of ferroelectricity. TbInO₃ crystal has great potential application in vortex memory. Full article

In this study, we report the successful growth of single crystals of a magnetic Weyl semimetal candidate NdAlGe with the space group I4₁md. The crystals were grown using a floating-zone technique, which used five laser diodes, with a total power of 2 kW, as the heat source. To ensure that the molten zone was stably formed during the growth, we employed a bell-shaped distribution profile of the vertical irradiation intensity. After the nominal powder, crushed from an arc-melted ingot, was shaped under hydrostatic pressure, we sintered the feed and seed rods in an Ar atmosphere under ultra-low oxygen partial pressure (<10⁻²⁶ atm) generated by an oxygen pump made of yttria-stabilized zirconia heated at 873 K. Single crystals of NdAlGe were successfully grown to a length of 50 mm. The grown crystals showed magnetic order in bulk at 13.5 K. The fundamental physical properties were characterized by magnetic susceptibility, magnetization, specific heat, thermal expansion, and electrical resistivity measurements. This study demonstrates that the magnetic order induces anisotropic magnetoelasticity, magneto-entropy, and charge transport in NdAlGe. Full article

The rapid growth of rutile TiO₂ single crystals through a laser floating zone (LFZ) method was demonstrated. LFZ has a higher power density, which is suitable for the growth of TiO₂ crystals with a high melting point. By optimizing the crystal growth parameters, including the growth rate, gas atmosphere, and rotation rate, the crystals could achieve their largest size of φ 9 mm × 25 mm, with a growth cycle of 12 h, and no cracks appeared. The properties of the obtained crystals were close to those of the crystals grown using other schemes, with a whole transmission range of 0.41–6.56 μm, thermal expansion coefficient of 9.92 × 10⁻⁶/K, and laser damage threshold of 1.44 GW/cm². The achieved results indicated that the crystals have high quality and good integrity when grown using LFZ and also imply a new choice for the rapid growth of rutile TiO₂ single crystals. Full article

An adaptation of the laser floating zone technique is used to modify the surface properties of ceramics with interest for biomedical applications. This new method is based upon the surface remelting of ceramic rods by using laser radiation, and its versatility is demonstrated in the surface structuring of two different eutectic composites with potential application as bone substitutes. Firstly, directionally eutectic rods of wollastonite (W)–tricalcium phosphate (TCP) and magnesium oxide (MgO)–magnesium stabilized zirconia (MgSZ) were grown by the laser floating zone technique. In the case of W-TCP eutectics, materials with crystalline, glass–ceramic, or vitreous microstructure could be obtained as the growth rate was increased. In the other case, a material made up of magnesium oxide and magnesium stabilized zirconia phases arranged in fibrillar or lamellar geometry was obtained. At higher solidification rates, the rupture of the growth front gave rise to the organization of the phases in the form of colonies or cells. The laser zone remelting technique was used to remove defects and to refine the microstructure of the directionally solidified eutectic surfaces as well as to cover MgO–MgSZ rods with W–TCP glass in the eutectic composition. The study provides a promising technique that can tailor the surface properties and functionality of bone repair materials. The products’ properties and challenges in preparation procedures are discussed. Full article

Cobalt-doped MgO-MgAl₂O₄ eutectic composites were explored for their use as selective emitters for thermophotovoltaic devices. Eutectic ceramic rods with different cobalt content were directionally solidified by using the laser floating zone technique at two processing rates to obtain microstructures with different domain sizes. Thermal emission between 1000 °C and 1500 °C and optical properties (reflectance and transmittance) at room temperature were measured in the Co-doped composites and the effect on microstructure and cobalt content was investigated. Thermal emission consisted of an intense broad band at about 1.67 µm matching with the bandgap of the InGaAs cell. The emission was ascribed to the de-excitation from the ⁴T₁(F) multiplet to the ⁴A₂(F) ground state of the thermally excited Co ions located in the tetrahedral sites of the MgAl₂O₄ phase. The selectivity of the thermal emission showed a decrease with the cobalt content due to the enhancement of other electronic transitions, which leads to keeping the cobalt content in these composites at low levels (<0.15% at Co) for their use as selective emitters. Full article