Processing technology, laser, optical and thermal properties of ceramic laser gain materials

Gadolinium has been frequently used in scintillators to enhance the X‐ray stopping power and in phosphors to improve the luminescent properties. In this paper, the fabrication of Gd3+‐substituted transparent (Y1−xGdx)3Al5O12 (x=0.01, 0.5, 0.75, and 1) ceramics via solid reactive sintering has been investigated. The effects of Gd3+ substitution on the phase evolution of the powder mixture, sintering behavior of the powder compact, and properties of the resultant ceramics were mainly demonstrated. It is shown that Gd3+ substitution favors the formation of kinetically stable intermediate compounds, particularly REAlO3 (RE=Y+Gd), and thus retards the crystallization of an RE3Al5O12 garnet. The samples of x=1 composition cracked upon vacuum sintering at temperatures above 1600°C, mainly due to the volumetric expansion induced by garnet formation. The transparent Y1.48Gd1.5Ce0.02Al5O12 ceramic (inline transmittance: ∼65% at 800 nm) vacuum sintered at 1700°C shows an emission band peaked at ∼570 nm upon UV excitation at 340 nm, exhibiting a red‐shift by ∼40 nm in comparison with the regular emission from YAG:Ce.

Section: Introductionmentioning

confidence: 99%

Effects of Gd³⁺ Substitution on the Fabrication of Transparent (Y_1−xGd_x)₃Al₅O₁₂ Ceramics

Xiu

et al. 2010

“…They showed that it was critical to dope Nd:YAG with 0.14 wt% SiO 2 (i.e., 0.5 wt% tetraethoxysilane [TEOS]) in order to achieve transmittance above 80%. A number of subsequent studies have shown that transparent polycrystalline Nd:YAG is equivalent to — and, in some cases, better than — single crystal Nd:YAG grown by the Czochralski method 6–11 . In the studies where the SiO 2 level was disclosed, the ceramic Nd:YAG was doped with 0.14 wt% SiO 2 .…”

Section: Introductionmentioning

confidence: 99%

Hot Isostatic Pressing of Transparent Nd:YAG Ceramics

Lee

Kupp

Stevenson

et al. 2009

Self Cite

155

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.

“…T he Y 3 Al 5 O 12 (YAG) is an important ceramic material, possessing excellent chemical stability, good creep resistance, and promising optical properties. A neodymium (Nd)‐doped YAG single crystal prepared by the Czochralski method has been the most widely used solid‐state laser material, finding wide applications in medical, materials processing, military, and scientific research 1,2 . Moreover, YAG ceramics are attractive as new transparent ceramics because of their optically isometric properties 3 .…”

Section: Introductionmentioning

confidence: 99%

Transparent Nd:YAG Ceramics Fabricated Using Nanosized γ‐Alumina and Yttria Powders

Xiu

et al. 2009

Neodymium (Nd):Y 3 Al 5 O 12 (YAG) ceramics of excellent transparency have been fabricated by solid-reactive sintering, using nanosized c-Al 2 O 3 and Y 2 O 3 powders as the starting materials. Reaction sequences and sintering behaviors of the powder mixture were characterized by X-ray diffractometry and dilatometry. One feature of the solid reactions involving c-Al 2 O 3 is the occurrence of hexagonal YAlO 3 , which is unstable and transforms to perovskite YAlO 3 (YAP) upon further heating. Because of the high reactivities of the starting nanopowders, a complete conversion of the powder mixture to YAG has been achieved by heating at 13001C for 4 h, via Y 4 Al 2 O 9 , hexagonal YAlO 3 , and YAP phases. In-line transmittances of the 1.5 at.% Nd:YAG ceramics (doped with 0.5 wt% of tetraethyl orthosilicate) at 700 nm are 81.0% and 65.7% after vacuum sintering at 17001 and 16001C for 5 h, respectively.