Yttrium oxide ceramics
Yttrium oxide (Y2O3) has a cubic structure, high melting point, good chemical and photochemical stability, wide optical transparency range, low phonon energy, and easy doping of rare earth ions. It has excellent plasma resistance and is ideal for semiconductor processing equipment applications where particle contamination must be avoided, because it can reduce equipment maintenance requirements, thereby increasing productivity.
Yttrium oxide transparent ceramics have excellent optical and thermal properties. It is a functional material with high application value. It has potential applications in high temperature windows, infrared hoods, luminescent media (flicker, laser and up-conversion luminescence) and semiconductor industries. Value has now become an alternative material for single crystals.
The main characteristics of the physical and chemical properties of yttrium oxide
①High melting point, good chemical and photochemical stability, and a wide range of optical transparency (0.23~8.0μm);
②At 1050nm, its refractive index is as high as 1.89, making it have a theoretical transmittance of more than 80%;
③Yttrium oxide has an effective tailoring from the larger hetero-band to the valence band, which is sufficient to accommodate the emission energy levels of most trivalent rare earth ions, so as to realize the multi-functionalization of its application;
④The phonon energy is low, and its maximum phonon cut-off frequency is about 550cm-1. The low phonon energy can suppress the probability of non-radiative transition, increase the probability of radiation transition, and improve the efficiency of luminous brightons;
⑤High thermal conductivity, about 13.6W/(m·K), high thermal conductivity is extremely important for its use as a solid laser cut-off material.
The above characteristics make yttrium oxide transparent ceramics have potential applications in high temperature windows, infrared detection, luminescent media, and semiconductor industries.
Sintering of yttrium oxide transparent ceramics
The preparation of yttrium oxide transparent ceramics mainly involves two aspects: powder and sintering technology:
In terms of powder, some are directly used commercial high-purity powder as raw material, and some are synthesized by wet chemical method, gas phase method, etc.;
In terms of sintering, the currently reported hot pressing sintering, hot isostatic pressing sintering, vacuum sintering and hydrogen atmosphere sintering (dry hydrogen, wet hydrogen), the densification mechanism can be summarized as pure solid-phase high-temperature sintering, liquid-phase sintering/ Transient liquid phase sintering, pressure assisted sintering and solid solution activated sintering. In order to improve the optical quality of yttrium oxide transparent ceramics and reduce the sintering temperature, a combination of multiple sintering methods is generally required.
Application research direction of yttrium oxide transparent ceramics
Due to its excellent physical and chemical properties, yttrium oxide is potentially developed in the fields of infrared windows and domes of missiles, visible and infrared lenses, high-pressure gas discharge lamps, ceramic scintillators and ceramic lasers.
① High-pressure gas discharge lamp tube: Yttrium oxide has a cubic phase structure, isotropic optical properties, high chemical stability, and can withstand the corrosion of sodium metal vapor and other metal halide vapors. It has always been used in the field of high-intensity gas discharge lamps. Although there is progress in the direction of the researchers' efforts, there are still factors such as technical cost and other constraints from the actual application and promotion.
②Window materials: Materials with good optical transmission performance in the range of 3~5μm have important applications in the military field. Although researchers have successfully developed yttrium oxide transparent ceramics with good transmittance through various sintering processes in the laboratory, However, because the current commercial nano-yttrium oxide powder contains many impurities, its optical performance cannot yet meet the actual application requirements.
③Y2O3-based scintillating ceramics: In the 1980s, researchers sintered (Y, Gd) 2O3: Eu, Pr transparent ceramics. The doping of Gd2O3 increases the density of the sample and also increases its X-ray absorption coefficient. Because of its high light output, short afterglow time and emission peak position matched with the detector, this material has been equipped as a ceramic scintillator. The annual output of X-CT produced by GE's medical department is measured in tons, and its commercial value is quite high.
④Up-conversion luminescence of Y2O3 transparent ceramics: Y2O3, as an excellent luminescent material matrix, has been used in the fields of fluorescent powder for lamps and electroluminescence for a long time. Studies have shown that Y2O3: also has a lower phonon energy (500㎝-1), which is equivalent to the current ZBLAN glass (a fluoride glass with a phonon energy of 500㎝-1) with higher up-conversion efficiency. Studies have shown that transparent yttrium oxide ceramics doped with different rare earth ions exhibit good up-conversion luminescence performance under 980nm LD excitation, and achieve up-conversion emission of multiple wavelengths such as blue, green, orange and red at 420-680nm.