In recent years, transparent terbium gallium garnet (TGG) ceramics have garnered significant interest for their application in high-power Faraday isolators. However, challenges in achieving high transparency have led researchers to explore the addition of various sintering aids as a key strategy to enhance the optical quality of TGG ceramics. Through this work, the effect of germanium (Ge) addition on the microstructure and optical transparency of TGG magneto-optical ceramics was investigated. TGG powders were synthesized by the co-precipitation method, and the source Ge was Ge ethoxide added through a ball-milling step. Transparent TGG ceramics were prepared by air pre-sintering combined with hot isostatic pressing post-treatment and subsequent annealing. The ceramics containing 200 ppm Ge exhibit optimal transmittance of 81.3% at 1064 nm (a value of theoretical transmittance), the Verdet constant was -133.0 radT-1m(-1) at 633 nm. When the addition of Ge reaches 600 ppm, a secondary phase can be observed on the surface of ceramic. Subsequently, TGG ceramics prepared from 1425 degrees C to 1500 degrees C with 200 ppm of Ge were analyzed, which revealed that the optimal pre-sintering temperature is 1450 degrees C.

Yb3+-doped (Lux,Sc1-x)2O3 materials demonstrate superior performance in generating short pulse lasers because of the broader emission spectra than single-component sesquioxide, making them a promising laser gain material for high-power ultrafast lasers. By adjusting the concentration of Lu/Sc, laser gain materials with different widths of emission spectra can be obtained. In this work, 5 at.% Yb:(LuxSc1-x)2O3 nano-powders with varying Lu concentrations (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9)were successfully synthesized by the co-precipitation method. Subsequently, Yb:(LuxSc1-x)2O3 transparent ceramics were produced through a combination of vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment at 1700 degrees C. Influence of Lu content on densification process, microstructure changes and optical transmittance of Yb:(LuxSc1-x)2O3 ceramics was investigated in detail. The average grain sizes of ceramics pre-sintered at 1700 degrees C decrease from 3.42 mu m to 1.43 mu m, and all ceramics have a relatively uniform microstructure. After HIP post-treatment, the optimum in-line transmittance of Yb:(LuxSc1-x)2O3 ceramics reaches 77.6 % at 1100 nm when x value = 0.1. With the increase of Lu content, the emission wavelength experiences a gradual blueshift from 1041 nm to 1034 nm. Notably, the Yb:(Lu0.6Sc0.4)2O3 ceramics exhibited the broadest emission bandwidth of 18 nm, which is 1.5 times of the Yb: Sc2O3, suggesting their immense potential for applications in ultrashort pulse lasers.

Recently, terbium gallium garnet (Tb3Ga5O12, TGG) ceramics have attracted significant attention as the primary material for Faraday isolators in high-power laser systems. In this work, TGG precursor was synthesized by the co-precipitation method. Thermal behavior, phase composition, and microstructure characterizations were conducted on the precursor and the TGG powder obtained by calcination. The effects of silicon sintering aids on the transmittance of TGG magneto-optical ceramics demonstrate that adding silicon can significantly enhance the optical transmittance of TGG ceramics. TGG ceramics with an addition of 200 ppm silicon, achieve the optimal in-line transmittance of 80.7 % at 1064 nm and 76.5 % at 633 nm after air annealing at 1100 degrees C, with the Verdet constant of -133.5 rad center dot T- 1 center dot m- 1 at 633 nm. Microscopy analyses confirm that the TGG ceramics exhibit neither secondary phases nor significant pores. The in-line transmittance and microstructure of TGG ceramics after annealing in air at 1000 degrees C were also investigated.

The 5 at.% Yb:CaF2 transparent ceramics were synthesized using a combination of hot pressing (HP) and hot isostatic pressing (HIP) from co-precipitated powders. The influence of varying HP pressures on the microstructure and laser performance of these ceramics was investigated. It was found that the optical quality of the CaF2 ceramics was significantly influenced by the HP pressure. Field emission scanning electron microscopy (FESEM) results indicated that HP pressure markedly affected the average grain size of the Yb:CaF2 ceramics. The sample that was hot pressed under 40 MPa and subsequently HIP post-treated at 600 degrees C for 3 h demonstrated the highest optical quality, achieving an in-line transmittance of 92.2 % at 1200 nm (2 mm thickness), with an average grain size of just 379 nm. Additionally, the ceramics processed under 20 MPa and then HIP post-treated at 600 degrees C showed superior laser performance, with a maximum output power of 1.25 W and a maximum slope efficiency of 13.5 %. This study offers valuable insights into the sintering mechanisms of fluoride-based ceramics and serves as a reference for enhancing the optical quality of Yb:CaF2 transparent ceramics.

Sc2O3, as a host for solid-state laser gain materials, has advantage of high thermal conductivity and easy matching with activating ions, which is promising in high-power laser applications. Currently, Yb-doped Sc2O3 ceramics have been fabricated at very high sintering temperatures, but their optical quality and sintering process still need further improvement. In this work, 5%Yb:Sc2O3 (in mass) nano-powders were obtained by co-precipitation, and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment. The cubic Yb:Sc2O3 nano-powders with good dispersity and an average crystallite of 29 nm were obtained. Influence of pre-sintering temperatures (1500-1700 degrees C) on densification process, microstructure changes, and optical transmittance of Yb:Sc2O3 ceramics was detected. Experimental data revealed that all samples have a uniform microstructure, while the average grain sizes increase with the increase of the sintering temperatures. Impressively, the optimum in-line transmittance of Yb:Sc2O3 ceramics, pre-sintered at 1550 degrees C after HIP post-treatment, reaches 78.1% (theoretical value of 80%) at 1100 nm. Spectroscopic properties of the Yb:Sc2O3 ceramics reveal that the minimum population inversion parameter beta 2 and the luminescence decay time of 5%Yb:Sc2O3 ceramics are 0.041 and 0.49 ms, respectively, which demonstrate that the optical quality of the Yb:Sc2O3 has been improved. Meanwhile, their best vacuum sintering temperature can be controlled down to a lower temperature (1550 degrees C ). In conclusion, Yb:Sc2O3 nano-powders are successfully synthesized by co-precipitation method, and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550 degrees C and HIP post-treatment.

The precursor of Gd2O2S:Pr,Ce powders with stacked layered structure was synthesized in hot water bath using oxide powders and concentrated sulfuric acid as raw materials. The powders were synthesized by calcining the precursor under flowing H-2 atmosphere at 500-900 degrees C for 3 h. The influence of calcination temperatures under hydrogen atmosphere, which was defined as reduction temperature, on the microstructures and properties of powders was investigated. Using the synthesized powders as initial material, Gd2O2S:Pr,Ce scintillation ceramics with high relative density (over 98 % of the theoretical value) were fabricated through vacuum pre-sintering at 1350 degrees C for 3 h followed by HIP post-treatment in an argon atmosphere at 1450 degrees C for 3 h. Intense green emission line at 511 nm due to the P-3(0)-> H-3(4) transition of Pr3+ was obtained in the X-ray excited luminescence (XEL) spectra of all Gd2O2S:Pr,Ce ceramics. The Gd2O2S:Pr,Ce ceramics fabricated from powders synthesized at 700 degrees C showed the highest optical transmittance, XEL intensity, and light yield (LY) value of 24,660 ph/MeV @ 662 keV gamma rays. The photoluminescence decay time of Pr3+ P-3(0) -> H-3(4) transition and scintillation decay time were measured to be similar to 3 mu s for all Gd2O2S:Pr,Ce ceramics. The effect of reduction temperature on optical transmittance and LY of Gd2O2S:Pr,Ce ceramics was also discussed.

Alumina transparent ceramics, which possess great optical, mechanical, and dielectric properties, provide potential for applications in cross fields such as optics and electronics. Submicron grained alumina transparent ceramics were successfully fabricated via air pre-sintering combined with hot isostatic pressing (HIP) using ZrO2 as a sintering additive. The influence of the ZrO2 content on the densification process, microstructure evolution and properties of alumina ceramics were investigated. The alumina ceramic sample with 500 ppm ZrO2 after HIP post-treatment at 1250°C for 3 h, has an average grain size of 0.89 μm, 54% smaller than that of ceramics without additive, in-line transmittance of 53.5% at 640 nm, bending strength of 592±33 MPa, Vickers hardness of 20.3±0.3 GPa, fracture toughness of 2.45±0.04 MPa-m1/2, and dielectric loss of 5.7×10-4.

Yb:CaF2 transparent ceramics represent a promising laser gain medium for ultra-short lasers due to their characteristics: low phonon energy, relatively high thermal conductivity, negative thermo-optical coefficient, and low refractive index. Compared to single crystals, Yb:CaF2 ceramics offer superior mechanical properties, lower cost, and it is easier to obtain large-sized samples with proper shape and uniform Yb3+ doping at high concentrations. The combination of air pre-sintering and Hot Isostatic Pressing (HIP) emerges as a viable strategy for achieving high optical quality and fine-grained structure of ceramics at lower sintering temperatures. The properties of the powders used in ceramic fabrication critically influence both optical quality and laser performance of Yb:CaF2 ceramics. In this study, the 5 atomic percentage (at.%) Yb:CaF2 transparent ceramics were fabricated by air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized through the co-precipitation method. The co-precipitated powders were optimized by studying air calcination temperature (from 350 to 550 °C). The influence of calcination temperature on the microstructure and laser performance of Yb:CaF2 ceramics was studied in detail. The 5 at.% Yb:CaF2 transparent ceramics air pre-sintered at 625 °C from powders air calcined at 400 °C and HIP post-treated at 600 °C exhibited the highest in-line transmittance of 91.5% at 1200 nm (3.0 mm thickness) and the best laser performance. Specifically, a maximum output power of 0.47 W with a maximum slope efficiency of 9.2% at 1029 nm under quasi-CW (QCW) pumping was measured.

Highly transparent 4.5 at.% Sm:YAG ceramics were fabricated by solid-state reactive sintering using tetraethyl orthosilicate (TEOS) and CaO as sintering additives. The influences of TEOS content on phase formation, microstructure evolution, and optical properties were investigated. The 4.5 at.% Sm:YAG ceramics with 0.3-0.6 wt% TEOS all have a single yttrium aluminum garnet phase after pre-sintering at 1725 degrees C for 30 h. With TEOS increasing from 0.3 to 0.6 wt%, residual pores were gradually discharged, the Sm:YAG ceramics with 0.5 and 0.6 wt% TEOS showed fully dense microstructure after vacuum sintering at 1725 degrees C for 30 h. After hot isostatic pressing (HIP) at 1750 degrees C for 3 h, the average grain size of the final Sm:YAG ceramics increased from 9.5 to 15.8 mu m with TEOS increasing from 0.3 to 0.6 wt%, and all the ceramic samples showed uniform microstructures. The 4.5 at.% Sm:YAG ceramics with 0.6 wt% TEOS achieved high in-line transmittance of 83.6% at 808 nm and absorption coefficient of 3.32 cm(-1) at 1064 nm, which means it can effectively suppress amplified spontaneous emission and parasitic oscillation.

Crystallized precursor with stacked layered was synthesized in hot water bath using oxide powders and concentrated sulfuric acid as raw materials. Gd2O2S powders with high phase purity were obtained by reducing the precursor under flowing hydrogen atmosphere. The influence of initial bath temperature of Gd2O3 and H2SO4 on the microstructure of Gd2O2S powders was investigated. The Gd2O2S:Pr,Ce powders showed a stacked layered structure and as the initial water bath temperature increases, the particle size of the flaky powders also increases. Using the synthesized powders, Gd2O2S:Pr,Ce scintillation ceramics were fabricated through pre-sintering in vacuum followed by HIP post-treatment in argon atmosphere. The Gd2O2S:Pr,Ce ceramics fabricated from the powders synthesized at lower initial water bath temperature show a rapid densification rate during pre-sintering. The Gd2O2S:Pr,Ce ceramic sample fabricated from powders synthesized at 7 degrees C showed the highest optical transmittance, XEL intensity, and light yield value of 25,800 ph/MeV @ 662 keV gamma rays. The PL decay time of Pr3+ P-3(0)-> H-3(4) transition was measured to be similar to 2.87 mu s for all ceramic samples. The effect of the initial water bath temperature on optical transmittance and light yield of Gd2O2S:Pr,Ce ceramics was also discussed.

(Sr0.97Eu0.01Dy0.02)Al2O4 persistent luminescence (PersL) ceramics were fabricated by solid-state reactive sintering in vacuum combined with hot isostatic pressing (HIP) using H3BO3 as a sintering additive. The phase composition, microstructure, luminescence properties, trap state, and PersL performance of HIP post-treated (Sr0.97Eu0.01Dy0.02)Al2O4 PersL ceramics were discussed. For the (Sr0.97Eu0.01Dy0.02)Al2O4 PersL ceramics after HIP post-treatment, the initial luminescence intensity of the ceramics reached over 6400 mcd/m(2) with simulated daylight irradiation of 1000 lx for 5 min, and the persistent emission decay time > 17 h. This is much better than the SrAl2O4:Eu2+,Dy3+ PersL powders and the other luminescent ceramics. In addition, this method is a solid-state reactive sintering method for synthesizing ceramics, which has the advantages of low cost and simple operation, and is suitable for large-scale, high-volume industrial production.

Gd2O2S:Tb nanopowders were synthesized in hot water-bath with the equal mole ratio of Gd2O3 and H2SO4 as raw materials. The influence of initial bathing temperature of Gd2O3 and H2SO4, which was defined as initial temperature, on the properties of precursors and powders was investigated. The precursors and Gd2O2S:Tb powders showed a layered structure, and all the reduced powders exhibit a pure Gd2O2S phase. With the increase of the initial temperature, the size and thickness of the flakes in the precursors and Gd2O2S:Tb powders increased. Using the obtained powders as starting materials, Gd2O2S:Tb scintillation ceramics were successfully fabricated by vacuum pre-sintering at 1250 degrees C for 3 h, followed by HIP post-treatment at 1450 degrees C for 3 h. The Gd2O2S:Tb ceramics from the powders prepared at lower initial temperature show a rapid densification rate during pre-sintering. The Gd2O2S:Tb ceramics from powders synthesized at 7 degrees C show the highest optical transmittance and XEL intensity, and the total transmittance of the ceramics with the thickness of 1.0 mm is 25.5% at 545 nm. The microstructures of the Gd2O2S:Tb ceramics from powders synthesized at different initial temperatures were also studied.