Hot Isostatic Pressing of Transparent Nd:YAG Ceramics

Abstract

This paper demonstrates that fine‐grained (2–3 μm), transparent Nd:YAG can be achieved at SiO2 doping levels as low as 0.02 wt% by the sinter plus hot isostatic pressing (HIP) approach. Fine grain size is assured by sintering to 98% density, in order to limit grain growth, followed by HIP. Unlike dry‐pressed samples, tape‐cast samples were free of large, agglomerate‐related pores after sintering, and thus high transparency (i.e., >80% transmission at 1064 nm) could be achieved by HIP at <1750°C along with lower silica levels, thereby avoiding conditions shown to cause exaggerated grain growth. Grain growth was substantially limited at lower SiO2 levels because silica is soluble in the YAG lattice up to ∼0.02–0.1 wt% at 1750°C, thus allowing sintering and grain growth to occur by solid‐state diffusional processes. In contrast, liquid phase enhanced densification and grain growth occur at ∼0.08–0.14 wt% SiO2, especially at higher temperatures, because the SiO2 solubility limit is exceeded.

Numerical simulation and experimental investigation on densification, shape deformation, and stress distribution of Ti6Al4V compacts during hot isostatic pressing

“…Hot isostatic pressing (HIP) as one of material processing approaches has been wildly used to fabricate near-net shape parts with near full density and high properties, which involves a process of high temperature and pressure with gas. This method can produce the hardcutting and precious metal and ceramic components directly from powders [3,4]. During HIP process, the porosity can be completely eliminated through the powder grain-coupled deformation mechanism [5]; however, the high pressure generally leads to severe deformation of the capsule.…”

Effect of Nd 3+ ions on phase transformations and microstructure of 0–4 at.% Nd 3+ :Y 3 Al 5 O 12 transparent ceramics

“…It was shown that pores with diameter <100 nm have the largest value of light scattering efficiency coefficient in the short wavelength range [47]. We believe that the optical quality of ceramics can be further improved by using of the hot isostatic pressing of ceramic samples [48]. Nevertheless, the obtained optical transmission of ceramics was near equal to that of corresponding Nd 3+ :YAG single crystals.…”

Fabrication of transparent ceramics by millimeter‐wave sintering

“…To this date, the most widely used method is high vacuum sintering in furnaces with Mo-W heating elements at a pressure of 1×10 -3 Pa and temperature in the range of 1600-1800 °С [2]. More technically sophisticated methods such as hot pressing (HP) [3] and hot isostatic pressing (HIP) [4] are used for sintering, as well as a combined method in which HIP follows the high vacuum sintering [5,6].…”