A New Chemical-Mechanical Polishing Method Based On Colloids Silica and MgO Was Developed For Polishing Y3Al5O12 Material

The material yttrium aluminum oxide (Y3Al5O12) is one of the materials commonly used in laser devices. For application in optical devices, it is necessary to produce ultra-precise surface quality, however, Y3Al5O12 material belongs to the group of difficult-to-machine materials with high brittleness and hardness. Therefore, it is very difficult to ensure that the main criterion when finishing this material to produce a quality surface in the nanometer form with the ability to remove the material is very difficult. To solve this problem, this work provided a new chemical - mechanical polishing mixture. The proposed polishing mixture of ZrO2, Na2SiO3–5H2O, and MgO abrasives has a weight ratio of 8%, 5% and 1% respectively, with the remainder being deionized water. The surface result after polishing is obtained with a material removed rate of 38 (nm/min) along with an ultra-smooth surface produced with Ra = 0.41 nm. With the help of X-ray photoelectron spectroscopy (XPS) method before and after polishing by CMS, the reaction mechanisms were elucidated. Analytical results show that Y3Al5O12 material produces YOOH and AlOOH in Na2SiO3 solution, then combines with –Si–OH to form (Y-Si) and (Al-Si) with significantly reduced hardness compared to other Y3Al5O12 materials, these products combine with MgO to form montmorillonites (3MgO–Al2O3–3SiO2–3Y2O3–5Al2O3). With this formation, the surface layer of Y3Al5O12 material becomes soft and is easily removed by ZrO2 abrasive particles under the influence of mechanical polishing, resulting in superfine surfaces are generated from the proposed CMS model.

Effects of sintering temperature on the microstructural properties of Al2O3–Y2O3 powder mixtures

In this study, YAlO3 (YAP) was produced at low temperatures by a powder sintering process. Al2O3–Y2O3 powder mixtures were subjected to heat treatment at different temperatures. The relationship between the sintering temperature and the emergence of new phases was investigated via X-ray diffraction, and supported by energy dispersive X-ray spectroscopy. The crystallization of the monoclinic yttrium aluminum oxide (Y4Al2O9) occurred at 1 000 °C, whereas the yttrium aluminum perovskite (YAlO3) crystallization occurred at 1 100°C. Energy dispersive X-ray spectroscopy analysis showed yttrium content in the sample containing Al2O3–YAlO3 powder sintered at 1100 °C, associated with the YAlO3 phase formed at this temperature. Brunauer–Emmett–Teller surface analysis showed a significant decrease in the pore volume of the sample sintered at 1 100°C.

Chemical gelation of cerium (III)-doped yttrium aluminium oxide spherical particles

A novel low-temperature (900 °C) chemical gelation method was developed to synthesize spherical and nonagglomerated Ce3+-doped yttrium aluminum oxide particles (YAG:Ce3+). This represents a process with a much lower processing temperature than current solid-state reaction processes (1400 °C). Characterization of the particles via x-ray diffraction and thermoanalytical methods showed that calcination at 900 °C for 2 h allowed direct crystallization from the amorphous phase, inferring that this process allows homogeneous mixing and increased precursor reactivity. Electron microscopy results showed that the spherical particles (∼100 to ∼3 μm) were the flocks of crystallites. The crystallite sizes (Rietveld refinement) grew linearly from 27 nm (900 °C) to 114 nm (1300 °C). The surface area decreased from 40 m2/g (900 °C) to 5 m2/g (1300 °C) because of the coagulating and growing of crystallites to bigger grains at 1300 °C. Single-crystal nanoparticles (around 100 nm) were obtained with this process and their atomic structures were revealed via high-resolution transmission electron microscopy.