Yttrium Aluminum Research Articles

Buried depressed cladding waveguides in neodymium-doped yttrium aluminate crystals fabricated by femtosecond laser writing: Raman properties and laser performance

Buried depressed cladding waveguides in neodymium-doped yttrium aluminate crystals fabricated by femtosecond laser writing: Raman properties and laser performance

High strength of SiC–AlN–TiB2–VC multiphase ceramics induced by interface reactions

In this work, SiC–AlN–TiB2–VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y2O3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al2O3 (on the surface of AlN) and Y2O3, which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB2, and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB2, and between TiB2 and VC. Al5C3N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B2O3 on the surface of TiB2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y2O3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa.

Interfacial reaction mechanism between Y-containing DD5 alloy and Al2O3 ceramic during directional solidification process

This study systematically investigated the influence of varying yttrium(Y) additions on the interfacial reaction mechanism between the DD5 superalloy melt and Al2O3-based ceramic molds during directional solidification. The analysis revealed the formation of a complex multilayer reaction layer at the alloy-ceramic interface. The interfacial products changed from CaO·6Al2O3 to a mixture of various yttrium oxides after Y was added. As the reaction time increased, the sequence of interfacial reaction products observed on the surface of Y-containing alloys progressed as follows: Y2O3, Y4Al2O9, YAlO3, and ultimately Y3Al5O12. Increasing the Y additions promoted the formation of a reaction layer with a higher atomic percentage of Y. The interfacial reaction process between the DD5 superalloy and Al2O3-based ceramic molds involved ceramic decomposition and diffusion, Y element diffusion and displacement reactions, Al2O3 dissolution and further diffusion of the Al element. This process resulted in the formation of different yttrium-aluminum oxides and related to the bidirectional erosion of the Y2O3. These interfacial reactions significantly contributed to the consumption of Y element within the alloy.

Structural and morphological studies on yttrium-doped magnesium aluminate spinel powders synthesized by mixed-fuel solution combustion synthesis approach

The incorporation of yttrium ions into the structure of magnesium aluminate spinel can be an effective approach to modify its microstructure, enhancing its formation, sintering behavior, and mechanical properties. In this work, a mixed-fuel solution combustion synthesis approach was used to prepare yttrium-doped spinel powders with the composition MgAl2-xYxO4 (x=0; 0.02; 0.06 and 0.10). It was shown that combustion of magnesium-, aluminum- and yttrium-nitrate salts solution in the presence of a mixture of specific fuels for each metal nitrate enables the direct production of crystalline spinels without the need for additional thermal treatment. Structural and morphological characterization showed that the main phase in all samples is a spinel phase (S.G. Fd3-m), while periclase (MgO), monoclinic yttrium aluminate (Y4Al2O9), and yttrium aluminum garnet (Y3Al5O12) were found in small portion in some samples. The average crystallite size increased in Y3+-substituted samples relative to undoped MgAl2O4, from 15 nm up to 40 nm. The lattice parameter increased with increase in yttrium content, ranging from 8.071 ? to 8.086 ?. The specific surface area of the synthesized powders spans from 8.2 m?/g for the undoped powder to 3.3 m?/g for the Y3+- substituted spinels with the maximum added yttrium content.

Effect of aluminum content on plasma resistance and contamination particle generation in yttrium aluminum oxide coatings

Yttrium aluminum oxide (YAO) has garnered interest due to its ability to protect the interior parts of process chambers from the corrosive effects of fluorine-based plasma. This ability is attributed to its low melting point, which enhances the internal bonding capabilities of the atmospheric plasma spray (APS) method. We explored the resistance of YAO coatings, with varying yttrium-to-aluminum content ratios, to fluorine-based plasma. These coatings were applied using the APS method and subsequently subjected to NF3/O2 gas. Our results revealed that a higher Al content ratio resulted in a decreased number of defects within the coating, which also led to selective etching at the initial Al2O3-rich sites, primarily creating relatively weak Al-F bonds and smaller particles. In particular, selecting an appropriate yttrium-to-aluminum content ratio significantly reduced the coating defects and enhanced the etch rate compared to coatings with a higher yttrium content ratio. This improvement was attributed to the balanced presence of Al-F and Y-F bonds. Furthermore, for coatings rich with the yttrium aluminum garnet (YAG) phase, the resistance to fluorine-based plasma was primarily influenced by the thickness of the APS-Y2O3 layer. This layer, used to augment adhesion to parts, relies on the low-temperature crystallization features of YAG. The findings of this study offer valuable insights for optimizing YAG coating in dry-etching processes requiring high-density APS coatings.

Temperature sensing technique across a wide range using phosphorescence intensity ratio of Dy3+-Doped YAG/YAP

To address the need for precise temperature measurement across an extended temperature range, we successfully synthesized a temperature-sensitive phosphorescent material using a high-temperature solid-state method. This material involves the incorporation of dysprosium dopant into the yttrium aluminum garnet/yttrium aluminum perovskite (YAG/YAP) phosphor matrix. Our primary objective was to leverage the phosphorescence intensity ratio of Dy3+ energy level transitions (4F9/2 → 6H15/2, 4I15/2 → 6H15/2) in response to temperature fluctuations, enabling temperature measurements within the 100–1300 °C range. Throughout our investigation, we observed shifts in the peak wavelengths “a” and “b” attributable to thermally coupled energy level transitions as temperature increased. Specifically, at 1000 °C, the peak wavelength “a” shifted from 457.4 nm to 457.8 nm, while at 750 °C, peak wavelength “b” shifted from 497.6 nm to 497.2 nm. Subsequently, we assessed the temperature sensitivity and measurement error of the sample. Impressively, the temperature sensitivity remained consistent across various single-pulse excitation powers and even after 50 h of continuous operation. The maximum absolute sensitivity exceeded 11.21 × 10−4 °C−1, and the relative sensitivity surpassed 2.78 × 10−2 %°C−1. The minimum temperature measurement error was approximately ±2 °C. As a result, the phosphorescent YAG/YAP: Dy3+ powder demonstrates significant potential for applications within the 100–1300 °C temperature range.

Influence of CeF3 on Ga2O3-Lu2O3-Al2O3-Y2O3-B2O3 glass for photonics material

CeF3 doped gallium lutetium aluminium yttrium borate glasses were investigated for photonics applications in this work. Their physical, structural, optical and luminescence properties were studied by the effect of CeF3 concentration. Glass density and refractive index raised with increasing CeF3 amount. The FTIR spectra and XRD pattern demonstrated that the glass network consisted of trigonal BO3 and tetragonal BO4 borate groups cooperating with metal oxides in amorphous nature, while CeF3 dopant acted as a glass modifier. Glass strongly absorbed the photons in ultraviolet region by transition of host component, superposed with the 4 f→5d transition of Ce3+ dopant. Under UV excitation, glass doped with 0.05 mol%-CeF3 performed the highest emission intensity at 391 nm by 5d→4 f transition. Due to the strong blue emission, half photons conversion ability and short decay time around 21 ns, this developed glass owns a potential for the blue light sources / medium and the ultraviolet to visible light converter.

Single-mode lasing in diode-pumped passive Q-switch lasers based on neodymium-doped yttrium aluminate and ytterbium-erbium glass active elements

Single-mode lasing in diode-pumped passive <i>Q</i>-switch lasers based on neodymium-doped yttrium aluminate and ytterbium-erbium glass active elements

The influence of thermal barrier coating (TBC) on diesel engine performance powered by using Mimusops elengi methyl ester with TiO2 nanoadditive

This current exploration aims for enhancing engine performance by using Mimusops elengi methyl ester 20% and 80% diesel with 25 ppm TiO2 [MEME20 + 25 ppm of titanium oxide] nanoparticle additive for the low heat rejection (LHR) engine. The coating of the piston crown was made with an insulation of two layers, initially, bond coat of nickel chromium aluminium yttrium (NiCrAlY) 50 µm and a topcoat 250 µm (5% yttrium + 2% neodymium oxide + 93% zirconium oxide) using the plasma spray coating technique. In comparison to diesel, the engine performance with MEME 20 + 25 ppm of titanium oxide resulted in enhancement in brake thermal efficiency (BTE) of 7.06% and a decrease in brake specific fuel consumption (BSFC) of 16.38%. The CO, HC and smoke values were curtailed by 35.66%, 31.8% and 19.66%, respectively, equated with diesel fuel. The NO x and EGT were increased by 22.23% and 9.33%, respectively, with full load at 1500 rpm.

The Optimization of Radiation Synthesis Modes for YAG:Ce Ceramics.

Synthesis in the radiation field is a promising direction for the development of materials transformation processes, especially those differing in melting temperature. It has been established that the synthesis of yttrium-aluminum ceramics from yttrium oxides and aluminum metals in the region of a powerful high-energy electron flux is realized in 1 s, without any manifestations that facilitate synthesis, with high productivity. It is assumed that the high rate and efficiency of synthesis are due to processes that are realized with the formation of radicals, short-lived defects formed during the decay of electronic excitations. This article presents descriptions of the energy-transferring processes of an electron stream with energies of 1.4, 2.0, and 2.5 MeV to the initial radiation (mixture) for the production of YAG:Ce ceramics. YAG:Ce (Y3Al5O12:Ce) ceramics samples in the field of electron flux of different energies and power densities were synthesized. The results of a study of the dependence of the morphology, crystal structure, and luminescence properties of the resulting ceramics on the synthesis modes, electron energy, and electron flux power are presented.

High-temperature oxidation and TGO growth behaviors of laser-modified YAG/YSZ double-ceramic-layer TBC

Yttrium—aluminum garnet/yttria-stabilized zirconia (YAG/YSZ) double-ceramic-layer thermal barrier coating (TBC) with NiCoCrAlY bond coating was deposited by atmospheric plasma spraying (APS) on Inconel 738 alloy substrate, and laser modification was carried out on the surface of YAG ceramic coating to improve the high- temperature oxidation resistance of TBC. Then, isothermal oxidation tests were designed to study the high-temperature oxidation and thermally grown oxide (TGO) growth behaviors of the as-sprayed (AS) and the laser modified (LM) YAG/YSZ TBC. Results show that TGO thickness and structure of both AS-TBC and LM-TBC exhibit the similar evolution trend, TGO thickness increases with the increasing of isothermal oxidation time, and TGO structure develops from single Al2O3 layer to the double-layer structure of upper mixed oxides and lower Al2O3. Because of the crucial inhibition effect of the laser modification on oxygen permeation, the appearance time of mixed oxides in LM-TBC is postponed, and the total TGO thickness of LM-TBC is reduced at the middle and final oxidation stages. The Al2O3 layer thickness proportion of total TGO in LM-TBC is always greater than or equal to that in AS-TBC at the same isothermal oxidation time. Compared with the AS-TBC, the parabolic oxidation rate of LM-TBC is decreased by 18.42%. Therefore, YAG/YSZ LM-TBC presents better oxidation resistance and lower TGO growth rate than AS-TBC.

Crystallographic, morphological and photoluminescent investigations of Tb3+ -doped YAlO3 perovskites for lighting applications.

Terbium(III)-doped yttrium aluminate perovskite (YAP:xTb3+ ) (x = 0.01-0.08 mol) was synthesized using a simple gel-combustion method. Structural elucidations were performed using X-ray diffraction (XRD) and Rietveld analysis. Fourier-transform infrared spectral studies validated the efficient synthesis of designed doped samples. Transmission electron microscopic images showed the agglomerated irregular dimensions of the synthesized nanocrystalline materials. When excited at 251 nm, a strong emissive line attributed to 5 D4 → 7 F5 electronic transition was observed at 545 nm (green emission). The maximum luminescence was found at the optimized concentration (0.05 mol) of Tb3+ ions; this emission was quenched by dipolar-dipolar (d-d) interactions. Chromaticity (x and y) and correlated colour temperature parameters were obtained by analysing the emission profiles. Finally, the colour coordinates of nanophosphors were closer to the National Television Standards Committee green coordinates, which replicates their potency in the design and architecture of R-G-B-based white LEDs.

Effect of Y2O3 additions on low cement high alumina refractory castable

ABSTRACT The effect of adding yttria (Y2O3) up to 2 wt.% on low cement high alumina castable is studied. Castable compositions with self-flowing and vibratable consistency (distribution coefficients, q = 0.21 and 0.29) are prepared using commercial raw materials and processed as per the conventional processing route, cured at 110°C, and fired at 1000 and 1550°C. An increase in yttria content is found to improve the physical and mechanical properties of castables for all temperatures. Phase analysis confirms the formation of the yttrium aluminate phase, and microstructural evaluation at 1550°C indicates enhanced bonding between the matrix and aggregate phase resulting in better density and strength properties.

Citrate-nitrate synthesis and understanding the properties of yttrium orthoaluminate-based luminophors

Using citrate-nitrate sol gel method, the authors obtained yttrium orthoaluminate with a perovskite structure YAlO3, as well as luminophors containing europium (III) ions Y1&ndash;хEuxAlO3 (x = 0.01; 0.025; 0.050; 0.075; 0.1). The conducted study helped understand the dynamics of phase and structural transformations that take place during yttrium orthoaluminate synthesis. Methods of thermal and X-ray phase analysis were used to establish the key stages of the synthesis process, and the Rietveld method based on ReX Powder diffraction software was used for quantitative evaluation. At the final process stage, sol forms, which then converts into gel and, when dried, forms xerogel. Heat treatment of xerogel leads to the decomposition of the organic framework and production of gaseous products. The solid phase interaction that takes place during YAlO3 synthesis involves stages at which yttrium &ndash; aluminium oxycarbonate Y3Al3O8CO3, as well as yttrium aluminates Y4Al2O9 and Y3Al5O12 form. Annealing at 1,300 oC for 7 hours enables to achieve the maximum concentration of orthoaluminate &ndash; i.e. 83% wt. Introduction of europium (III) ions stabilizes the perovskite structure, and the mass fraction of YAlO3 in the final product rises as the concentration of europium(III) ions rises. The maximum concentration of the target phase is 96 wt.%, achieved when 0.1 mol Eu3+ is introduced into the matrix. The surface morphology of yttrium aluminate was studied by scanning electron microscopy. Particles of similar grain size and shape can be obtained when conducting the synthesis at 1,300 oC. The authors examined the luminescence properties of yttrium orthoaluminate-based crystalline phosphors. Luminophors containing Eu3+ ions and having the following composition: Y1&ndash;хEuхAlO3 (x = 0.01; 0.025; 0.050; 0.075; 0.1), emit red light, which is typical of Eu3+ in crystal matrices. The Y0,9Eu0,1AlO3 luminophor has the maximum emitted intensity. Support for this research was provided under the Development Programme of&nbsp;the Tomsk State University Priority 2030.

Effects of YH2 addition on pressureless sintered AlN ceramics

A new type of non-oxide sintering additive of YH2 was introduced for the fabrication of AlN ceramics with high thermal conductivity and flexural strength. The effects of YH2 addition (0–5 wt%) on the phase composition, densification, microstructure, thermal conductivity and flexural strength of pressureless sintered AlN ceramics were investigated and compared with those Y2O3-added samples (1–5 wt%). The addition of 1 wt% YH2 led to an in-situ reduction reaction with oxygen impurities, the formation of Y2O3 and finally the formation of yttrium aluminate, which in turn improved densification and microstructure. A high flexural strength (408.69 ± 28.23 MPa) was achieved. The addition of 3 wt% YH2 increased the average grain size and purified the lattice. All these effects are believed to help achieve a high thermal conductivity of 184.82 ± 1.75 W·m−1·K−1. Although the thermal conductivity was close to the value of 3 wt% Y2O3-added sample, its strength was much increased to 381.53 ± 43.41 MPa. Meanwhile, it demonstrated a good combination of the thermal conductivity and flexural strength than the values reported in some literature. However, further increasing the YH2 addition to 5 wt% resulted in a high N/O ratio that inhibited the densification behavior of AlN ceramics. The current study showed that AlN ceramics with excellent thermal and mechanical properties could be obtained by the introduction of a suitable YH2 additive.

Mitigating CMAS Attack in Model YAlO3 Environmental Barrier Coatings: Effect of YAlO3 Crystal Orientation on Apatite Nucleation

Environmental barrier coatings (EBCs) are used to protect ceramic-matrix composites from undesirable reactions with steam and calcia–magnesia–alumina–silicate (CMAS) particulates found in gas-turbine engine environments. Effective EBCs contain yttria or rare earth ions that will react with molten CMAS to form a protective apatite layer that prevents further attack. Methods to improve the EBCs’ CMAS mitigation capabilities focus on improving the apatite yield but neglect optimizing the apatite formation behavior. This study investigates the effect of apatite nucleation behavior on CMAS penetration by comparing the CMAS attack at 1350 °C of four different single crystal orientations of yttria aluminate perovskite (YAP), a promising EBC candidate. The EBC/CMAS interfacial energy and, thus, reaction behavior varies with YAP orientation. In regions with low CMAS loading, rapid apatite growth is seen on YAP substrates with orientations associated with high EBC/CMAS interfacial energy. However, CMAS penetration is most significant in these samples because the apatite growth is facilitated by recession of the YAP substrate nearby. Such behavior is not observed in regions with high CMAS loading where small apatite crystals form on top of an yttrium aluminate garnet (Y3Al5O12, YAG) phase. This study shows that strategies that control the nucleation and growth of apatite will provide better protection against CMAS.

The impact of yttrium aluminum garnet stoichiometry deviation on the conversion efficiency of tetravalent chromium ions

In this work, the conversion efficiency of Cr4+ ions and the optical properties of ceramics based on chromium-doped yttrium aluminum garnet were investigated. Increasing the conversion efficiency of Cr3+ to Cr4+ opens up broad prospects for using YAG ceramics as saturable absorbers for passive Q-switching of Nd- and Yb-solid-state lasers. The aim of this work was to study the effect of magnesium oxide concentration on the conversion efficiency of Cr3+ to Cr4+ under conditions of Al3+ (4.8 mol.%) and Y3+ (2.9 mol.%) cations excess in the garnet structure as well as the stoichiometric ratio Y3+/Al3+ = 3/5. The possibility of changing the concentration of Cr4+ ions in both the octahedral and tetrahedral positions due to the formation of magnesium substitution defects when the composition deviates from the yttrium-aluminum garnet stoichiometry has been studied. Chromium-doped transparent optical ceramics based on yttrium-aluminum garnet with different ratios of Y3+/Al3+ cations was obtained by the two-stage coprecipitation method. Magnesium oxide was used as a sintering additive and charge compensator for converting chromium ions from the trivalent to the tetravalent state in concentrations of 0 to 0.2 wt.%. It was found that aluminum excess in the yttrium-aluminum garnet matrix leads to a decrease in the Cr3+ to Cr4+ conversion efficiency. A deviation of stoichiometry towards an excess of yttrium leads to a decrease of air annealing temperature for oxidizing chromium ions to the tetravalent state and their transition to the tetrahedral position. However, the samples optical transmittance with an excess of yttrium was lower than in the cases of an excess of aluminum and stoichiometry. It was found that with an increase in the vacuum sintering temperature from 1780 to 1820 °C in the samples with an excess of aluminum, an increase in the concentration of Cr4+ ions in the tetrahedral position occurs, as evidenced by higher absorption intensity at a wavelength of 1030 nm. For the cases of stoichiometry and an excess of yttrium in garnet, this effect is less pronounced. Samples of optical ceramics of yttrium-aluminum garnet with a light transmission of more than 75 % in the visible and near-IR ranges with pronounced absorption bands of chromium have been obtained. The results of the work can be applied to the creation of passive switches for solid-state lasers.

Improved additive manufacturing of silicon carbide parts via pressureless electric field‐assisted sintering

High solids loading silicon carbide (SiC)-based aqueous slurries containing only .5 wt. % organic additives were utilized to create specimens of various geometries via an extrusion-based additive manufacturing (AM) technique. Pressureless electric field-assisted sintering was performed to densify each specimen without deformation. The combination of these techniques produced parts with >98% relative density despite containing only 5 wt.% oxide sintering additives. After sintering, specimens contained only the α-SiC and yttrium aluminum perovskite phases. This suggests the evolution of a nonequilibrium yttrium aluminate phase, as well as transformation from β-SiC to α-SiC. The fabrication method presented in this work has advantages over other AM techniques commonly used with SiC, because it does not require significant organic additives nor additional postprocessing steps such as chemical vapor infiltration or polymer impregnation and pyrolysis.

A comparative study of the properties of yttrium and lanthanum aluminates obtained by Pechini sol–gel process

The optical and photocatalytic properties of yttrium and lanthanum aluminates obtained by Pechini sol-gel process were studied by comparison. The aluminates were characterized by XRD, TEM, SEM, DRS, FTIR and PL spectroscopy. The photocatalytic properties were investigated in the removing of both cationic and anionic dyes from aqueous solutions. A higher photocatalytic activity was identified for yttrium aluminate (90% - 97% after 90 min), with the maximum value for methylene blue solution (97.15%), and a photocatalytic activity of 46.88% was determined for lanthanum aluminate in the degradation of methylene blue. The photocatalytic activity was in a good correlation with the aluminates optical behavior.

Yb-doped Y–Al–O thin films with a self-organized columnar structure and their anti-Stokes photoluminescence properties

We fabricated ytterbium-doped yttrium aluminum oxide (Yb:Y–Al–O) thin films by radio-frequency magnetron sputtering and evaluated their crystallinity and anti-Stokes photoluminescence (PL) properties for optical refrigeration. The Yb:Y–Al–O films that were grown on c-sapphire substrates had better transparency than the films deposited on fused-quartz substrates. The better transparency is considered to be a result of the smaller mismatch between the thermal expansion coefficients of Yb:Y–Al–O and c-sapphire. We found that the thin films on the c-sapphire substrates consist of densely packed sub-micron columnar crystals that are aligned perpendicular to the substrate. In these films, we confirmed the existence of perovskite, garnet, and monoclinic phases despite using a single-phase sputtering target. The excitation wavelength dependence of anti-Stokes PL is used to investigate the energy transfer process between trivalent Yb ions in neighboring columnar crystals. The data indicate that the resonant energy transfer from Yb3+ ions at a specific seven-coordinated site of the monoclinic phase to Yb3+ ions in neighboring columnar crystals is faster than the radiative relaxation at the energy-donor site.