Search

Laser grade 7 at.% Er:Y 2 O 3 transparent ceramics with submicron grain size were fabricated by using one-step vacuum sintering followed by hot isostatic pressing (HIPing) technique. Through studying the sintering trajectory of Er:Y 2 O 3 ceramics, the sintering temperature zone where sufficient relative density (>96%), no pore-boundary separation, and sub-micron grain size (<1 μm) ceramic samples could be identified. The samples pre-sintered in this zone were readily densified by HIPing. To maximum the densification and achieve high transparency, it is critical to suppress the final-stage grain growth. After HIPing at 1520 °C, the Er:Y 2 O 3 ceramics were fully densified without further grain growth, and exhibited in-line transmission of about 81.6% at 2000 nm. Continuous wave (CW) room temperature laser operation of the Er:Y 2 O 3 transparent ceramic at 2.7 μm was demonstrated. [ABSTRACT FROM AUTHOR]

Abstract 5 at.% Yb:Y 2 O 3 transparent ceramics were fabricated using vacuum sintering plus HIP. The ceramics doped with 1 at.% ZrO 2 as the sintering additive were densified at 1700 °C in vacuum followed by HIPing at 1775 °C, while those without sintering additives were densified at 1520 °C in vacuum followed by HIPing at 1450 °C. After sintering, both ceramics had relatively high in-line transmittance. However, during laser experiments, the ZrO 2 -doped Yb:Y 2 O 3 (Zr-YbY) ceramics were photodarkened when irradiated by 940 nm pump light. The discoloration might be attributed to the formation of Zr3+ color centers during lasing. In contrast, no photodarkening effect was detected in the pure Yb:Y 2 O 3 ceramics without sintering additives (P-YbY). The P-YbY ceramics exhibited much higher lasing efficiency (17%) than the Zr-YbY ceramics (9%). To our best knowledge, it is the first time that the photodarkening effect was detected in rare-earth doped sesquioxide laser ceramics. [ABSTRACT FROM AUTHOR]

Abstract Highly sinterable Y 2 O 3 nano-powder with low degree of agglomeration was synthesized by using a spray precipitation technology, without the use of any additives and dispersants. Compared with the precursor made by using the dripping method (D-precursor), the precursor made by the spraying method (S-precursor) had much lower degree of hard agglomeration. So did the resultant calcined Y 2 O 3 powder (S-Y 2 O 3 powder) as compared with the D-Y 2 O 3 powder. Sintering behaviors of the two powders were studied. Ceramics made from the S-Y 2 O 3 powder (S-Y 2 O 3 ceramics) showed much higher densification rate and final density. After vacuum sintered at 1650 °C for 5 h, relative density of the D-Y 2 O 3 ceramics was merely 97.3%, while that of the S-Y 2 O 3 ceramics reached 99.5%. In addition, the D-Y 2 O 3 ceramics cannot be sintered to 98% relative density by using the vacuum sintering technique, due to the high degree of agglomeration of the D-Y 2 O 3 powder. Moreover, the S-Y 2 O 3 ceramic exhibited homogeneous microstructure and an in-line optical transmittance of 81.6% at 1200 nm after HIP treatment. The spray precipitation method should be applicable to synthesizing other oxide powders. [ABSTRACT FROM AUTHOR]

0.7 at.% Ho:Y 2 O 3 transparent ceramics were fabricated by using vacuum sintering plus hot isostatic pressing (HIPing) process. Vacuum sintered at 1500 °C for 12 h followed by HIPing at 1450 °C for 4 h, the Ho:Y 2 O 3 ceramics showed excellent in-line transmission and uniform grain size, with an average grain size of about 1 μm. The Ho:Y 2 O 3 ceramics showed good thermal conductivity thanks to the identical effective ionic radius between Ho 3+ and Y 3+ . For the first time, room temperature laser oscillation from Ho:Y 2 O 3 transparent ceramics was demonstrated. The uncoated 0.7 at.% Ho:Y 2 O 3 ceramic slabs were in-band pumped by a Tm:fiber laser at 1941 nm, and a maximum output power of 1.3 W at 2116.8 nm was achieved with a slope efficiency of 31.2%. It indicates that Ho:Y 2 O 3 transparent ceramics could be excellent laser gain medias for 2 μm solid-state laser applications. [ABSTRACT FROM AUTHOR]

Ho:Y 2 O 3 ceramics were prepared using co-precipitated powders, with ammonium sulfate as dispersant. Y 3+ was co-precipitated together with Ho 3+ and Zr 4+ to produce precursors, which were calcined at 1100–1400 °C to produce yttria-based powders. At calcination temperatures of ≤1300 °C, agglomeration of powders was not observed. When the temperature was increased to 1400 °C, severe agglomeration was detected. Densification was closely related to the calcination temperature: a lower calcination temperature resulted in a faster densification of ceramics to the relative density of 99.7%. The ultimate densification to ~100% was also closely related to powders' impurity level and agglomeration. Grain growth was mainly determined by sintering temperature, but not by the initial crystallite size of powders. The optimal calcination temperature was 1300 °C, at which the obtained Ho:Y 2 O 3 powder was free from agglomeration. Using this powder, the resultant Ho:Y 2 O 3 ceramics showed pore-free microstructure and good optical transparency. [ABSTRACT FROM AUTHOR]