The Mechanism And Technical Studies Of Improving The Transmittance Of Laser Ceramics

Transparent Nd:YAG(neodymium-doped yttrium aluminum garnet) laser ceramics is a laser gain medium which has excellent properties. Not only does it has an excellent light transmittance performance which is similar to single crystal, but also it has properties such as high strength, high hardness, corrosion resistance, high-temperature resistance, which is like ceramics and far better than other normal materials. Because of the characteristic of ceramics, it has advantages in terms of component designing and structure, which is beneficial to optimize the laser performance and develop new function, thus it gets wide attention.In this thesis, transparent 1% Nd:YAG laser ceramics was fabricated by a solid-state vacuum sintering method,which is using high-purity commercial yttria、 alumina, neodymia as raw material, TEOS and MgO as sintering aids. Before the sintering process, we have studied the pretreatment of the Y2O3 power and the fabrication of high-dispersion Y2O3 nano-powder by the directional precipitation method. Then a series of contrast experiments about the different kinds and the amount of the sintering additives have been conducted to find the optimal combination. During the sintering, we have researched the influence of sintering holding time on the transmittance of samples and analyzed the surface morphology, element composition and transmittance of the samples by scanning electron microscope (SEM), uv-vis spectrophotometer and other technical means. Then we analyze the transmittance curves at 400 nm. Finally we get the following conclusions:1. The appropriate pretreatment of Y2O3 powder can eliminate the gap and pore existing in the particles in some degree. The too low treatment temperature does not much affect the Y2O3 powder, but the too high treatment temperature can promote grain growth, it will reduce the sintering activity and increase the agglomeration.2. Well-size-distributed Y2O3 nano-powder can be achieved by the directional precipitation method. The Y2O3 powder presents as little ball and has a high specific surface area which is beneficial to increasement of the sintering activity and sintering process in theory.3. A series of contrast experiments about the sintering additives combination has been conducted and finally we get the optimal additives combination is 1%TEOS and 0.3%MgO, then we have discussed the working mechanism of them respectively.4. The transmittances of samples which have different sintering holding time are different, and it rises with the extended holding time within certain limits. In consideration of energy saving and low cost, we think the sintering holding time of 30h is the best choice, and under the circumstances we get the sample which has a highest transmittance of 75%.5. Combined with related theory about scattering, we have analyzed the transmittance curves at 400nm. We think the value of the transmittance curves at 400nm is sensitive to the existence of tiny pores, and we can use it as one of the parameters that characterize the existence of tiny pores.