Abstract
Y2O3:Yb3+ 5 at% ceramics have been synthesized by the reactive sintering method using different commercial yttria powders (Alfa-Micro, Alfa-Nano, and ITO-V) as raw materials. It has been shown that all Y2O3 starting powders consist from agglomerates up to 5–7 µm in size which are formed from 25–60 nm primary particles. High-energy ball milling allows to significantly decreasing the median particle size D50 below 500 nm regardless of the commercial powders used. Sintering experiments indicate that powder mixtures fabricated from Alfa-Nano yttria powders have the highest sintering activity, while (Y0.86La0.09Yb0.05)2O3 ceramics sintered at 1750 °C for 10 h are characterized by the highest transmittance of about 45%. Y2O3:Yb3+ ceramics have been obtained by the reactive sintering at 1750–1825°C using Alfa-Nano Y2O3 powders and La2O3+ZrO2 as a complex sintering aid. The effects of the sintering temperature on densification processes, microstructure, and optical properties of Y2O3:Yb3+ 5 at% ceramics have been studied. It has been shown that Zr4+ ions decrease the grain growth of Y2O3:Yb3+ ceramics for sintering temperatures 1750–1775 °C. Further increasing the sintering temperature was accompanied by a sharp increase of the average grain size of ceramics referred to changes of structure and chemical composition of grain boundaries, as well as their mobility. It has been determined that the optimal sintering temperature to produce high-dense yttria ceramics with transmittance of 79%–83% and average grain size of 8 µm is 1800 °C. Finally, laser emission at ∼1030.7 nm with a slope efficiency of 10% was obtained with the most transparent Y2O3:Yb3+ 5 at% ceramics sintered.
Highlights
Yttrium oxide ceramics doped with trivalent ytterbium ions (Y2O3:Yb3+) are currently investigated as promising material for the development of active media for solid-state lasers, especially for operation in high-power short-pulse generation mode [1,2,3]
The aggregates of yttria particle have a complex hierarchy structure and contain a large number of cracks between adjacent blocks. This structure is typical for the powders obtained by chemical precipitation method, and the presence of cracks is due to the removal of gaseous products during precursor crystallization
In the second part of our work we report the synthesis of yttrium oxide ceramics using complex sintering additives La2O3+ZrO2 with the lowest total concentration ever reported (2 at%) [32]
Summary
Yttrium oxide ceramics doped with trivalent ytterbium ions (Y2O3:Yb3+) are currently investigated as promising material for the development of active media for solid-state lasers, especially for operation in high-power short-pulse generation mode [1,2,3]. [6], Y2O3:Yb3+ ceramics were produced by combining hot pressing and hot isostatic pressing of co-precipitated nanopowders coated with LiF sintering aid. The use of high concentrations of La2O3 sintering additive may be accompanied by formation of cracks [19], or disorder glass-like structure [20] in ceramics To overcome these problems, complex sintering aid La2O3+ZrO2 has been utilized [21,22,23,24,25,26]. The effect of different starting materials of yttrium oxide on formation of Y2O3:Yb3+ transparent ceramics by the reactive sintering has been studied for the first time; the evolution of the microstructure and optical properties of ceramics as a function of processing conditions are determined
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