| Ytterbium doped scandium oxide?Yb:Sc2O3?have been considered as a promising high-powder laser gain materials for its high thermal conductivity.However,it is very difficult to fabricate Yb:Sc2O3 single crystal with large size and excellent quality due to the high melting temperature?about 2430 oC?.Yb:Sc2O3 transparent ceramics with high quality can be fabricated at lower sintering temperature.Therefore,Yb:Sc2O3 transparent ceramics have been considered to be an alternative since high optical transparency can be achieved by using nano-powders as raw materials.In this paper,high quality 5at%Yb:Sc2O3 nano-powders were synthesized by co-precipitation method.First of all,the influences of molar ratio between the M3+(Sc3+ and Yb3+)and precipitant?R value?on phase composition and micromorphology of the calcined powders were studied.The results showed that the R value will affect the micromorphology and agglomeration of resultant powders.When R value was 4.0,the 5at%Yb:Sc2O3 powders possess highest dispersibility and sinterability.Then,the influence of calcination temperature on the degree of crystallinity,micromorphology of resultant powders and microstructure and optical quality of 5at%Yb:Sc2O3 transparent ceramics were systematically investigated.The results showed that the degree of crystallinity,the particle size and agglomeration of 5at%Yb:Sc2O3 nano-powders increased with the increasing of calcination temperature.The 5at%Yb:Sc2O3 transparent ceramics were sintered from the nano-powders calcined at various temperatures.The transmittance of the ceramic samples increases with the calcination temperature from 600 to 1100 oC,whereas the transmittance decreases rapidly when the temperature increases to 1200 oC.The in-line transmittance of 5at%Yb:Sc2O3 ceramics calcined at 1100 oC exhibits the value of 56.7% at 1100 nm.As a results,1100 oC was found to be the optimal temperature for preparation of 5at%Sc2O3 powders.Then the 5at%Yb:Sc2O3 transparent ceramics were fabricated by vacuum sintering method.The effects of sintering temperature and time on the optical quality and microstructure of ceramic samples were studied.The results showed that the optical quality can be improved with increasing the sintering temperature and time.The grain size increases with the sintering temperature.5at%Yb:Sc2O3 transparent ceramics with in-line transmittance of 73.9% at 1100 nm and average grain size of 182 ?m were fabricated by vacuum sintering of the optimal powder at 1850 oC for 10 h.At last,the spectroscopic properties and the gain characteristics of obtained 5at%Yb:Sc2O3 transparent ceramics were also studied.The absorption cross sections appear at 941 nm 975 nm with values of 0.56×10-20 cm2 and 0.82×10-20 cm2,respectively.The large absorption cross section and broad absorption band make it suitable for pumping by a laser diode with no need for accurate temperature control.The emission cross-section of 5at%Yb:Sc2O3 transparent ceramics were calculated by Reciprocity Method,The largest emission cross section occurs at 1041 nm with a value of 1.14×10-20 cm2.The corresponding gain cross section??g?of the 5at%Yb:Sc2O3 transparent ceramics can be calculated from the absorption and emission cross section.The minimum ?min?1041 nm?is determined to be 0.036.The results above showed that the 5at%Yb:Sc2O3 transparent ceramics was an excellent laser gain material. |
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