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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]

Transparent 0.6 at% Nd:Y2O3 ceramics were fabricated by vacuum sintering at 1550°C and hot isostatic pressing (HIP) at 1540°C. The ceramics sintered at such temperatures had good homogeneity with dense microstructures, without any residual pores and secondary phases. The in‐line transmittance reached 81.6% at 1000 nm and remained 81.1% at 650 nm. Continuous wave (CW) laser operation of an uncoated ceramic slab was evaluated. A maximum output power of 3.6 W with slope efficiency of 45.2% at 1.08 μm was obtained. [ABSTRACT FROM AUTHOR]

This paper reports on the influence of rapid rate sintering (RRS) on densification and microstructure evolution of yttria transparent ceramics by using vacuum sintering. The presence of temperature gradient has been confirmed during the RRS process. The higher the heating rate (HR), the larger the temperature gradient in the samples would be. By using RRS, e.g., HR = 40°C/min, the samples could be densified very fast to a relative density of 99.6%. However, these samples could not be further densified, due to the presence of difference in densification caused by a heating rate-induced temperature gradient. By using a two-step RRS with an intermediate-temperature thermal treatment, this problem has been successfully addressed. The intermediate-temperature treatment allowed for the particle neck growth, so that effective thermal conductivity of the compacts was increased greatly. Therefore, the temperature gradient and differentiate densification were effectively prevented. Samples sintered using the two-step RRS process could be fully densified and excellent in-line optical transmittance was achieved. It is believed this strategy is applicable to other transparent ceramics, as well as other engineering ceramics. [ABSTRACT FROM AUTHOR]

Highly transparent 0.5 at.% Tm:Y2O3 ceramics were prepared by using solid-state reaction combined with vacuum sintering method, with ZrO2 and Al2O3 as sintering aids. Doping amount of ZrO2 was fixed at 1 at.%, while the effect of Al2O3 on densification, microstructure evolution, and transmittance of the Y2O3 ceramics was carefully studied. It was found that the addition of Al2O3 was very effective in improving densification of Y2O3, due to the formation of an Al-rich eutectic phase Y4Al2O9 ( YAM) during the sintering process. As the content of Al2O3 was increased from 0 to 81.8 wt ppm, porosity of the ceramics was decreased and transmittance was increased. However, when the content of Al2O3 was increased to 137 wt ppm, a secondary phase began to segregate at grain junctions. Further increase in the amount of Al2O3 led to an increase in both amount and size of the secondary phase. At the optimized content of Al2O3 with 81.8 wt ppm, the Tm:Y2O3 ceramics sintered at 1860°C for 13 h exhibited an in-line transmittance of 83.0% at 2000 nm and 76.5% at 600 nm. It is expected that this finding can be readily applied to other transparent ceramics. [ABSTRACT FROM AUTHOR]