Y2O3 Transparent Ceramics Research Articles

Mechanical and optical properties of spark plasma sintered transparent Y2O3 ceramics

Commercial Y2O3 nanopowder was used to fabricate transparent Y2O3 ceramics by spark plasma sintering under the pressure of 100MPa for 20min with the heating rate of 100°C/min. The microstructures, mechanical and optical properties of the Y2O3 ceramics sintered at different temperatures were investigated in detail. Densification occurred up to a sintering temperature of 1500°C, and above 1500°C, rapid grain growth and pore growth occurred. The highest relative density of 99.58% and the minimum average grain size of 0.58±0.11µm were obtained at 1500°C. The flexural strength, hardness and fracture toughness of the optimal spark plasma sintered Y2O3 ceramic were 122MPa, 7.60GPa and 2.06MPa.m1/2, respectively. The Y2O3 ceramic sintered at 1500°C had the in-line transmission of about 11–54% and 80% in the wavelength range of 400–800nm and 3–5µm, respectively.

Fabrication and properties of Y2O3 transparent ceramic by sintering aid combinations

Transparent Y2O3 ceramics were fabricated by the solid-state reaction and vacuum sintering method using La2O3, ZrO2 and Al2O3 as sintering aids. The microstructure of the Y2O3 ceramics sintered from 1550°C to 1800°C for 8h were analyzed by SEM. The sintering process of the Y2O3 transparent ceramics was optimized. The results showed that when the samples were sintered at 1800°C for 8h under vacuum, the average grain sizes of the ceramics were about 3.5µm. Furthermore, the transmittance of Y2O3 ceramic sintered at 1800°C for 8h was 82.1% at the wavelength around the 1100nm (1mm thickness), which was close to its theoretical value. Moreover, the refractive index of the Y2O3 transparent ceramic in the temperature range from 30°C to 400°C were measured by the spectroscopic ellipsometry method.

High-Resolution Optical Line Width Measurements as a Material Characterization Tool

We present a case study on Eu3+-doped Y2O3 transparent ceramics in which high-resolution laser spectroscopy is used as a material characterization tool. By comparing the results from coherent and incoherent optical spectroscopy with other characterization methods, we show that optical techniques can deliver supplementary information about the local environment of the activator ions in materials. Thus, high-resolution spectroscopy may be of interest for the investigation of a wider range of rare earth doped optical materials beyond materials studied for quantum information technology. The refinement of optical spectroscopy for the study of narrow optical transitions in rare earth ion single crystals has demonstrated that these techniques are extremely sensitive tools for probing the local environment of the rare earth ion. These techniques, such as photon echo experiments, have been important in developing materials for quantum information technology and spectral filtering applications. Here, we apply thes...

Effect of surfactant concentration and solvent used for washing in the preparation of Yb:Y2O3 transparent ceramics

Effect of surfactant concentration and solvent used for washing in the preparation of Yb:Y2O3 transparent ceramics

Optical absorption and mechanism of vacuum-sintered ZrO2-doped Y2O3 ceramics

ZrO2 is considered an efficient sintering additive for transparent Y2O3 ceramics. However, the doping of tetravalent Zr4+ ions leads to a dark brown color of the ceramic after vacuum sintering. In this study, the optical properties of vacuum-sintered and air-annealed ceramics were characterized using transmittance spectra and a Commission International de l’Eclairage (CIE) diagram. The corresponding defects are investigated by electron paramagnetic resonance (EPR) spectra. The band gap of the vacuum-sintered samples is 2.72eV, which is much smaller than that of the annealed sample. The results reveal that the VO+ (F+ center) and Zr3+ defects form transition energy levels near the top of the valence band and at the bottom of the conduction band, respectively. The color-related absorption is mainly attributed to the electronic transfer from the Zr3+ level to the conduction band and from the F+ center to the Zr3+ level.

Yb:Y2O3 transparent ceramics processed with hot isostatic pressing

Highly transparent 5 at.% Yb:Y2O3 ceramics were fabricated by using a combination method of vacuum sintering and hot isostatic pressing (HIP). Co-precipitated Yb:Y2O3 powders, with 1 at.% ZrO2 as the sintering aid, were used as the starting material. The Yb:Y2O3 ceramics, vacuum sintered at 1700 °C for 2 h and HIPed at 1775 °C for 4 h, exhibited small grain size of 1.9 μm and highly dense microstructure. In-line optical transmittance of the ceramics reached 83.4% and 78.9% at 2000 and 600 nm, respectively. As the ceramic slab was pumped by a fiber-coupled laser diode at about 940 nm, a maximum output power of 0.77 W at 1076 nm was achieved, with a corresponding slope efficiency of 10.6%.

Fabrication of transparent La-doped Y2O3 ceramics using different La2O3 precursors

Despite being the most common sintering additive of transparent Y2O3 ceramics, La2O3 still suffers from weight changes when used in manufacturing processes due to its absorption of moisture and carbon dioxide. In the present work, two stable precursors, La(OH)3 and La2O2CO3, were proposed for use as sintering additives for transparent Y2O3 ceramics; La2O3 powder was used for comparison. A series of experiments were conducted to investigate the influences of La2O3, La(OH)3 and La2O2CO3 on the optical properties of Y2O3 ceramics by comparing the properties of mixed powders, green bodies and their sintering behaviors. Samples using La(OH)3 or La2O2CO3 as sintering additives exhibited more favorable optical properties at similar sintering temperatures compared to those using La2O3. Transmittances close to the theoretical value at 4μm were achieved for samples doped with La(OH)3 or La2O2CO3 sintered at 1800°C.

Dispersion of nano-sized yttria powder using triammonium citrate dispersant for the fabrication of transparent ceramics

In the present work, transparent Y2O3 ceramics were prepared via colloidal processing method from nano-sized Y2O3 powders. The effects of triammonium citrate (TAC) on the colloid stability of aqueous suspensions of nano-sized Y2O3 powders were studied. The surface properties of yttria powders were notably affected by the addition of TAC dispersant. The adsorption of TAC on the particle surface shifts the IEP to lower pH values and increases the absolute zeta potential in alkaline region. Rheological characterization of the investigated system revealed an optimal dispersant concentration of 1wt%, which correlated well with the saturation adsorption of TAC on Y2O3 powder surfaces. The suspensions with solid loadings up to 35vol% were achieved with further addition of Tetramethylammonium hydroxide (TMAH) into the dispersing system. The consolidated green bodies were treated by cold isostatic pressing to further increase the green density. Transparent Y2O3 ceramics were prepared after vacuum-sintering at 1700°C for 5h. The transmittances of the sample were 74.5% at 800nm and 79.8% at 2000nm, respectively.

Up-conversion and near infrared luminescence in Y2O3: Er3+, Yb3+ transparent ceramics

Er[Formula: see text]/Yb[Formula: see text] co-doped Y2O3 transparent ceramics were fabricated by vacuum sintering method. The Y2O3: Er[Formula: see text]:Yb[Formula: see text] nonopowders were prepared by co-precipitation method in advance. The morphology of powders and ceramics as investigated. The powders exhibited well dispersive condition with 100[Formula: see text]nm in diameter. The compactness of ceramics increased obviously with the increasing temperature. No pore was found in the ceramic sintered at [Formula: see text]C. The ceramic samples showed intense near infrared luminescence peaking at 1535[Formula: see text]nm under the excitation of 980[Formula: see text]nm lasers, assigned to the [Formula: see text] transition of Er[Formula: see text]. The intense up-conversion emissions were observed under the excitation of 980[Formula: see text]nm and 1550[Formula: see text]nm lasers.

Effect of γ-Al2O3 additives on the microstructure of Y2O3 ceramics

This paper reported the fabrication of Y2O3 transparent ceramics with γ-Al2O3 doped as the sintering aid under vacuum using the co-precipitated Y2O3 powders as raw materials. The different concentrations of γ-Al2O3 were employed for investigating the effect on the microstructures and densities of Y2O3 ceramics. The doped sintering aid could achieve fine microstructure and high density. The average grain sizes were around 25 μm, and the relative densities were all above 98.5 %. The best sample was achieved with 0.08 wt% γ-Al2O3 when sintered at 1850 °C for 8 h. And the grain size and relative density were 25 μm and 99.47 %, respectively.

High optical quality Y2O3 transparent ceramics with fine grain size fabricated by low temperature air pre-sintering and post-HIP treatment

High optical quality Y2O3 transparent ceramics with fine grain size were successfully fabricated by air pre-sintering at various temperature ranging from 1500 to 1600°C combined with a post-hot-isostatic pressing (HIP) treatment using co-precipitated powders as the starting material. The fully dense Y2O3 transparent ceramic with highest transparency was obtained by pre-sintered at 1550°C for 4h in air and post-HIPed at 1600°C for 3h (the pressure of HIP 200MPa), and it had fine microstructure and the average grain size was 0.96μm. In addition, the in-line transmittance of the ceramic reached 81.7% at 1064nm (1mm thickness). By this approach, the transparent Y2O3 ceramics with fine grain size (<1.6μm) were elaborated without any sintering aid.

Fabrication of submicron-grained IR-transparent Y2O3 ceramics from commercial nano-raw powders

In this study, we successfully optimized the ‘pre-sintering-hot-isostatic pressing’ (HIPing) combined process, yielding infrared (IR)-transparent Y2O3 ceramics with a homogeneous submicron grain size. Green bodies were pre-sintered in a two-step process in a vacuum furnace under various sintering conditions to obtain a high enough density with restrained grain growth for a subsequent HIPing treatment. The effects of the pre-sintering conditions on the density and grain size of the samples were analyzed in detail. It was found that during the pre-sintering process, dramatic grain growth occurs from the surfaces of the samples when the density reaches about 95%, after which it spreads over the entire sample. For a sample pre-sintered at a T1 temperature of 1700°C and a T2 temperature of 1550°C for 5h, after annealing in air and subsequent HIPing, good IR-transparency (i.e., transmittance of a 1-mm-thick sample at 2500nm of 73%) was achieved without significant grain growth (average grain size of 0.37μm).

Effects of pre-sintering and annealing on the optical transmittance of Zr-doped Y2O3 transparent ceramics fabricated by vacuum sintering conjugated with post-hot-isostatic pressing

In this work, Zr-doped Y2O3 transparent ceramics were fabricated by vacuum pre-sintering at various temperatures ranging from 1650 to 1800°C combined with a post-hot-isostatic pressing (HIP) treatment. The pre-sintered samples all show black opaqueness mainly due to the formation of oxygen vacancies, which can be removed by post-annealing in air. The HIP treatment can also eliminate the blackness as well as residual pores, giving rise to optical transparency. The in-line transmittance of the samples after HIP was found to depend strongly on the microstructure of the as-sintered samples. The optimal microstructure of these types of samples before the HIP treatment should be fine grained with only intergranular pores, which can easily be removed by HIP. Annealing before HIP was shown to be necessary to enhance the transmittance of the samples. The effects of the pre-sintering heating rate on the optical transmittance of the HIP-treated samples were also studied.

Vacuum sintering of transparent Cr:Y2O3 ceramics

0–0.7 at% Cr:Y2O3 transparent ceramics were prepared by vacuum sintering. The optimum in-line transmittance in the visible and near infrared region is 78%, and the Vickers hardness of the sintered 0.1 at% Cr:Y2O3 is 10.1GPa, respectively. The mechanism of Cr-doped and the optical properties has been discussed. The results indicated that the Cr:Y2O3 transparent ceramic is a promising laser material with enhanced mechanical property.

Dependence of spectroscopic and thermal properties on concentration and temperature for Yb:Y2O3 transparent ceramics

High transparency ytterbium doping yttria (Yb:Y2O3) ceramics were fabricated by vacuum sintering. The influence of temperature and doping concentration on optical and thermal properties of Yb:Y2O3 ceramics were evaluated. The increased Yb doping concentration causes the red-shift of absorption edge. The intensities of absorption peaks increase linearly with Yb3+ ion concentration, and the absorption cross-section at ∼978nm is calculated to be 1.15×10−20cm2. When Yb3+ doping content is 5.0at.%, the strongest peak centers at the wavelength of 1030nm with the full width at half maximum (FWHM) of 17nm, and stimulated emission cross-section is measured to be 1.58×10−20cm2. Both absorption coefficient and fluorescence lifetime increase with increasing Yb3+ concentration. The optimum doping concentration of Yb3+ ion in Y2O3 transparent ceramic is in the range of 5.0–7.0at.%. For 5.0at.% Yb:Y2O3 transparent ceramic, as temperature increases from 10K to room temperature (RT), the fluorescence intensity decreases and the peaks are broaden.

Luminescence and thermal lensing characterization of singly Eu3+ and Tm3+ doped Y2O3 transparent ceramics

Transparent Y2O3 ceramics singly-doped with either Eu3+ or Tm3+ were fabricated by means of sequential consolidation steps at high pressure and temperature. These ceramics were characterized for their luminescence and thermal lensing behaviors, and the results compared to data on single crystals reported in literature. Thermal diffusivity, D, and conductivity, K, values of D=26×10−3cm2/s and K=5.8W/mK, respectively, for 1.0mol% Eu3+ and 0.5mol% Tm3+ singly-doped Y2O3 transparent ceramics were obtained. These values are about half of those for single crystal analogs. A small temperature coefficient of the optical path length change, ds/dT=3×10−6K−1, was determined, making these materials suitable for applications requiring nearly athermal response. Selected spectroscopic properties were obtained by means of Judd–Ofelt analysis and together with thermal lens results provided absolute values for the fluorescence quantum efficiency of several levels, particularly 62% for the 5D0 level of Eu3+ and 84% for the 3F4 level of Tm3+.

Energy transfer mechanisms of quantum cutting near infrared luminescence in Ho3 +/Yb3 + co-doped Y2O3 transparent ceramics

Blue to near infrared quantum cutting luminescence has been achieved in the Ho3+/Yb3+ co-doped Y2O3 transparent ceramics upon the 449nm excitation. Based on the steady and the dynamic emission spectra and the energy level diagrams of Ho3+ and Yb3+, the energy transfer between Ho3+ and Yb3+ was proposed to be first via the Ho3+: 5F4, 5S2+Yb3+: 2F7/2→Ho3+: 5I6+Yb3+: 2F5/2 cross relaxation, then followed by the efficient energy transfer from Yb3+: 2F5/2 to Ho3+: 5I6, and further the enhanced Ho3+: 5I6→5I8 transition emitting at 1206nm.

Fabrication of transparent Y2O3 ceramics via aqueous gelcasting

Transparent Y2O3 ceramics were successfully prepared via aqueous gelcasting and vacuum sintering. A novel and simple gelling system was employed using a nontoxic and water-soluble copolymer, acting as both a dispersant and a gelling agent in air at room temperature. Surface treatment was carried out by a nucleophilic addition reaction to prevent hydrolysis of Y2O3 powder. The rheological behavior of Y2O3 slurries was evaluated to optimize the dispersant content as well as solids loading. After dried and presintered, the cast bodies were sintered at 1850°C for 6h in vacuum. Transparent Y2O3 ceramics were obtained with a homogeneous microstructure and as high as 80.9% in-line transmittance at 1100nm (1mm thick).

Optical and scintillation properties of Sc2O3, Y2O3 and Lu2O3 transparent ceramics synthesized by SPS method

Sc2O3, Y2O3 and Lu2O3 transparent ceramics were prepared by the spark plasma sintering (SPS) method. After polishing, the samples were semitransparent. Their optical transmittance was 10–40% at 500 nm which corresponded with their semi-transparency. In the X-ray induced emission spectra, a broad emission peak appeared around 335 nm in each sample. For this wavelength, scintillation decay time for Y2O3 and Sc2O3 were 22 and 48 ns, respectively. The light yield of Sc2O3, Y2O3 and Lu2O3 was 16,200, 2600, and 200 ph/5.5 MeV-alpha, respectively, which followed from the alpha-ray induced pulse height spectra. The gamma-ray induced light yield of Sc2O3 was 11,500 ph/MeV, which is 1.4 times larger than that of conventional single crystal BGO (Bi4Ge3O12) scintillator. Light yield non-proportionality and energy resolution of Sc2O3 were examined for the first time.

Yttrium oxide transparent ceramics by low-temperature microwave sintering

Yttrium oxide (Y2O3) transparent ceramics samples have been successfully fabricated by microwave sintering processing at relatively low temperatures. In comparison with the vacuum sintering processing, Y2O3 transparent ceramics can be obtained by microwave sintering at lower sintering temperature and shorter sintering time, and they possess higher transmittances and mechanical properties. The technologies of low-temperature microwave sintering and the relationships of the microstructures and properties of the specified samples have been investigated in detail. We have found out that the low-temperature microwave sintering technique has its obvious advantages over the conventional methods in manufacturing yttrium oxide transparent ceramics.