(Lu_1-xSc_x)₂O₃ High Transparency Preparation And Performance Research Of Laser Ceramics

With the rapid development of solid state laser in the direction of high power and ultrashort pulse lasers,it is urgent demand to develop new laser gain medium with high-performance.(Lu1-xScx)2O3(Lu2O3?Sc2O3 and their mixed crystal)shows good thermal and thermo-optical properties,low maximum phonon frequency for oxide matrices,and broad spectral bands for RE3+ions.Therefore,it is recommended as one of the most promising solid laser medium.However,it is extremely difficult to grow(Lu1-xScx)2O3 single crystals with conventional crystal growth techniques because of their high melting points.Transparent ceramics have been proposed as an alternative to enable easier and size-scalable production.Besides,laser ceramics also have high uniformity.Flexible preparation and other merits.In this point of view,the research on(Lul1-xScx)2O3 laser ceramics has its significance.As the performance of(Lu1-xScx)2O3 ceramics is based on high transparency,a systematic study was carried out to achieve the high transparency and high performance of(Lu1-xScx)2O3 ceramics.High sintering activity(Lu1-xScx)2O3 powder is crucial to the realization of highly transparent ceramics.Although a small amount of ceramic powders can be obtained by precipitation method,it still need to be improved for it is still lack of practical,reliable and widely accepted specific methods.And the contradictions between synthetic efficiency and high quality haven't been effectively solved.The essential reason of ceramics powder inhomogeneity lies in the inhomogeneity of the precipitation reaction process.Therefore,we introduced a new idea-"micro zone reaction" to control the inhomogeneity of the precipitation reaction process and improve the powder properties.Meanwhile,much of reactions were parallel generated to realize high efficiency.Based on these ideas,a new spray precipitation device was invented.Lu2O3 and Sc2O3 powders were synthesized with high efficiency and high quality in this work.A systematic study was made to explore the basic physicochemical mechanisms of the Lu2O3 and Sc2O3 liquid precipitation,the formation of a precursor,phase transformation and morphology evolution.The influence mechanism of spray rate and alcohol/water ratio on powder properties were studied in detail.Through this work,it was discovered that the composition and properties of the precipitate could be controlled effectively by proper spray rate.And the introduction of anhydrous ethanol could improve the uniformity of the Sc2O3 powder.Using improved precipitation method with reverse and forward titration,Lu2O3 and Sc2O3 nano powders with high purity.narrow particle distribution and good dispersibility were obtained.It established the foundation for high transparency sintering of(Lu1-xScx)2O3 ceramics.Besides,this method was successfully extended to synthesis YAG nano powders with good dispersibility.In the study of the(Lu1-xScx)2O3 sintering,a new high-efficiency doping method was adopted to find and solve the contradictions fundamentally between introducing a mass of heterogeneous sintering aid for improving transparency and the lase performance degradation resulted from a mass of heterogeneous sintering aid.Firstly,a novel co-doped LiF and zirconia method have been used.The new method can improve the optical properties of ceramics and reduce the use of the heterogeneous sintering aids.Secondly,a novel and highly effective aid Al2O3 was doped to suppressed the excessive growth of the grains and improve the SC2O3 sintering.The transparent Sc2O3 ceramic samples with a excess 80%transmittance have been prepared by this method.Ultimately,RE:(Lu1-xScx)2O3 ceramics were prepared by hot isostatic pressing without any sintering aids.The study was made on controlling the design of the RE:(Lu1-xScx)2O3 components to modify the sintering activity.The sintering mechanism of as-prepared powders,impact of the parameter x on transparency sintering and the concentration of RE3+were systematic researched.The systematic study shows that the x can promote the grain grow when its value is small,but when x increasing,the effect turns to restrain the grain grow.However,the effects of RE3+concentration depends on the radius difference of the remaining matrix ions and the comprehensive effect of concentration contrast,which has different regulating and sintering effects under different conditions.The impacts of x values and doping concentrations on microstructures and properties have been studied.Through delicately regulating,the highly transparent Ho:(Lu1-xScx)2O3,Er:(Lu1-xScx)2O3,Tm:(Lu1-xScx)2O3 and Tm,Ho:(Lu1-xScx)2O3 ceramics have been prepared.The optical properties of the high-quality(Lu1-xScx)2O3(LuScO)ceramics as prepared were studied.A novel transparent 4.76 at%Tm:(Lu2/3Sc1/3)2O3 "mixed" sequioxide ceramic is synthesized by hot isostatic pressing(HIP).The spectroscopic properties of the Tm3+ ion are described within the Judd-Ofelt theory,which resulted in intensity parameters of ?2=2.429,?4=1.078 and ?6=0.653[10-20 Cm2].For the 3F4?3H6 transition,the maximum stimulated-emission cross-section ?sE is 7.15×10-21 cm2 at 1951 nm.The radiative lifetime of the 3F4 state is 4.01 ms.Under diode-pumping at 802 nm,a microchip Tm:(Lu2/3Sc1/3)2O3 ceramic laser generated?1 W at 2100 nm with a slope efficiency of 24%.The spectroscopic and laser properties of the Tm:(Lu2/3Sc1/3)2O3 ceramic are compared with those of a Tm:LuScO3 single crystal.The ceramic exhibits very broad and flat gain cross sections,which is promising for ultrashort pulse generation.The Tm-doped mixed sesquioxide ceramic laser is mode-locked near 2?m using InGaAsSb quantum-well semiconductor saturable absorber and chirped mirrors for dispersion compensation.Maximum average output power of 175 mW is achieved for a pulse duration of 230 fs at a repetition rate of 78.9 MHz with a 3%output coupler.Applying a 0.2%output coupler pulses as short as 63 fs are generated at 2.057?m.Novel transparent Ho-doped sesquioxide ceramics are synthesized by the Hot Isostatic Pressing technique.Under GaSb diode-pumping at 1.929?m,the 1.4 at%Ho:LuScO ceramic laser generated 187 mW of quasi-continuous wave(CW)output at 2.114-2.135?m with a slope efficiency ?of 7.6%.Under diode-pumping at 980 nm,the 7 at%Er:LuScO ceramic laser generated 12.6 W of peak power output at 2.8?m.