MgO-CaO-Fe2O3-x wt.% SiO2-y wt.% Al2O3-z wt.%Y2O3 (3 <= x <= 15, 0 <= y <= 12, 0 <= z <= 12) porous ceramics are prepared by the organic foam template method and the mechanical and thermal performance are investigated. The XRD results illustrate that the main phase is MgO, and the secondary phases include MgSiO3, MgAl2O4, and Y2O3. The Mg-O-Si and Mg-O-Y peaks are observed in FTIR spectrum, indicating the successful incorporation of additives. The results from mercury intrusion porosimetry show that the porous ceramic is mainly macro-pores, with few meso-pores distributed on the skeleton, which effectively increase total porosity. The SiO2 doping changes the fracture manner of MgO-CaO-Fe2O3 ceramic from intergranular to transcrystalline, co-addition of Al2O3 can promote the formation of MgAl2O4 spinel that distribute at the grain boundary and decrease grain size of MgO, and the Y2O3 could enable uniform grain size distribution, which disperse external forces evenly to improve the mechanical properties. The MgO composite ceramic synthesized by organic foam template method, due to the high total porosity similar to 85%, exhibits thermal conductivity below 0.07 W/(m.K), which is almost independent of SiO2-Al2O3-Y2O3 doping concentration. Typically, the MgO-2.5 wt.% CaO-1 wt.% Fe2O3-3 wt.% SiO2-0.3 wt.% Al2O3-6 wt.% Y2O3 porous ceramics exhibit total porosity of 84.6%, compressive strength of 4.3 MPa, and thermal conductivity of 0.063 W/(m.K). Benefiting from their outstanding compressive strength and low thermal conductivity, the MgO based porous composite ceramics exhibit significant potential for application as building insulation materials.

BaO-CaO-Al2O3-SiO2 (BCAS) glass systems have attracted considerable attention as sealing and bonding materials for high-temperature electronic packaging due to their tunable viscosity, thermal expansion compatibility, and good chemical stability. This research utilised BCAS glass powders with 5 wt.% MgO, CaO, and Al2O3 additives to create glass-bonded junctions with AlN ceramics at various bonding temperatures (1000-1030 °C). The influence of oxide additions and bonding conditions on joint tensile and shear strengths was methodically examined, revealing that Al2O3 emerged as the most potent additive due to improved glass network connectivity. Significantly, the incorporation of Al2O3 enhanced wettability and aligned thermal expansion, allowing for a tensile strength of 20.7 MPa to be maintained at 500 °C. Stress distribution examination indicates that significant stress concentration is present in the peripheries of the bonding interface, which markedly affects the fracture characteristics of the joints. The findings offer understanding regarding the correlation among glass composition, bonding characteristics, and the mechanical durability of BCAS glass sealing systems.

By introducing a new gas pressure assisted sintering (GPAS) method, the evolution of microstructure, mechanical properties, and thermal conductivity of AlN ceramic were investigated. In the GPAS process, high pressure promotes particle rearrangement and enhanced the densification and mechanical performance of AlN ceramic with small grain size at lower sintering temperature, which was in accordance with Hall-Petch empirical formula. After sintering with GPAS method, the flexural strength of AlN ceramic peaked at 515.7 MPa, which exhibited a 27.7 % increase compared with flexural strength (403.9 MPa) of the conventional pressureless sintered AlN ceramics. Typically, the AlN ceramic, sintering at 1700 degrees C for 6 h under N2 atmosphere with a pressure of 0.2 MPa, displayed relative density of 99.04 %, three-point flexural strength of 486.7 MPa, Vickers hardness of 10.71 GPa, thermal conductivity of 174.6 W/(m center dot K), showing excellent comprehensive properties.

The black porous alumina ceramic vacuum chuck device with excellent optical, electrical and mechanical properties, applying for wafer holding operation, was designed and fabricated in this research. MnO2 was doping into the Fe2O3-CoO-NiO-Al2O3 system to form spinel and regulate the optical and electrical performance of the Al2O3 matrix. The conversion of Mn4+ to Mn3+ and Mn2+ facilitates d-d transitions within the crystal field, thereby enhancing the absorbance of visible light (VIS). As the MnO2 content increased to 8 wt%, the light absorptivity was greater than 91 % in the VIS range (91.8%@456nm). The volume resistivity of the ceramic changed from the order of 1015 S2 cm to 1011 S2 cm due to large number of charge carriers brought by defective spinel. As the pore-forming agent PMMA (Polymethyl Methacrylate) content increased to 30 %, the porosity of the porous ceramic reached to 41 %, the light absorptivity was greater than 83 %, the volume resistivity was 6.8 x 1012 S2 cm, and the compressive strength was 141 MPa. Moreover, the vacuum chuck, assembled from porous alumina ceramic with 41 % porosity and effective area of phi 80 mm, can adsorb smooth sample more than 729 g stably, which exhibited excellent adsorption stability. This work successfully achieved synergistic optimization of optical, electrical, and mechanical performance in vacuum chuck, which provided an excellent candidate device for semiconductor processing industry.

With the rapid development of the semiconductor integrated circuits, higher optical, electrical, and mechanical properties of vacuum chucks are required to prevent the influence of light reflection, avoid the breakdown of component from electrostatic accumulation and ensure wear resistance to extend its service life. In this paper, MnO2 is introduced to Al2O3-Cr2O3-TiO2 composite to form lattice defective spinel to regulate the optical, electrical, and mechanical properties of alumina ceramics via vacuum sintering. The X-Ray diffraction (XRD) results reveal that the phase of composites are Al2O3 and spinel, with a noticeable leftward shift trend of spinel's diffraction peaks corresponding to larger lattice constants. The X-ray photoelectron spectroscopy (XPS) analysis confirms the increase of Mn3+, Mn2+, and Vo, where Mn3+ replaces Al3+ in the spinel, resulting in an increase in the lattice constant. Additionally, the aliovalent ionic substitution formed oxygen vacancy (Vo) introduces defect energy levels and decreases band-gap energy (from 1.332 to 1.248 eV), which significantly enhances the light absorption performance of black alumina ceramics in the UV-VIS-NIR range. Moreover, the Vo acts as the path of free electrons in the material, thereby reducing its volume resistivity to 7.06 x 1011 S2 cm. Although the existence of defects leads to stress concentration, the mechanical property of black ceramics remain satisfactory due to the smaller grains. As the MnO2 content is 1.5 wt%, the absorptivity is greater than 85 % in the UV-VIS-NIR range (91.7 %@564 nm), and the volume resistivity, hardness, fracture toughness are 6.53 x 1012 S2 cm, 13.12 GPa, 2.36 MPa m1/2 respectively, which provides a candidate material for vacuum chuck applying in semiconductor manufacturing.

When preparing aluminum oxynitride (AlON) transparent ceramics from Al2O3-AlN slurries by direct ink writing (DIW), green bodies need long drying duration to guarantee uniform water evaporation but AlN hydration will happen, creating extra alumina content and deteriorating the optical properties of AlON. Being capable of dissolving a portion of Al2O3, MgAl2O4 was doped to prepare AlON transparent ceramics through reactive sintering using DIW technology. With 79 wt% solid-content aqueous slurries, AlON gradually becomes single phase with densities around 3.69 g/cm3 after MgAl2O4 content and sintering temperature regulating, resulting in a substantial enhancement in optical transmittance. Through transmission electron microscopy analysis, MgAl2O4 helps reduce the internal stress in AlON lattice, diminishing lattice distortion and enhancing transmittance. However, MgAl2O4 addition also results in grain size increase and decreases mechanical properties of AlON. This study provides a new approach to solve AlN hydration when preparing AlON transparent ceramics by DIW from Al2O3-AlN aqueous slurries.

Aluminum nitride (AlN)-based ceramics have emerged as a leading material choice for next-generation electrostatic chucks (ESCs) in semiconductor equipment, owing to their unique combination of high thermal conductivity and tunable electrical characteristics. In this study, La2O3 and MgO co-doped AlN ceramics were synthesized by hot-pressed sintering at 1750 degrees C, which controls the electrical properties of AlN ceramics by suppressing grain defects and forming dispersed secondary phase at the grain boundaries, to meet the application requirements at high temperatures. The ceramics deliver exceptional performance, fully satisfying ESC application requirements, with a thermal conductivity of 72.8 W m(-1) K-1 and resistivity of 10(9)similar to 10(10) Omega cm (from 400 to 550 degrees C). This work demonstrates a synergistic enhancement of high-temperature electrical conductivity in AlN-based ceramics, paving the way for novel strategies to design high-performance engineering ceramics.

The effects of TiO2 content and sintering temperature on the electrical and mechanical properties of the alumina ceramics prepared via vacuum sintering were investigated. The sample comprises the phases of Al2O3, MgAl2O4, and Al2TiO5. Under vacuum sintering conditions, oxygen atoms in TiO2 detach from the crystal lattice, forming quasi-free electrons, oxygen vacancies and Ti3+, thereby reducing the volume resistivity of alumina ceramics. XPS (X-ray photoelectron spectroscopy) analysis revealed that the increasing TiO2 content facilitates the transformation of Ti4+ to Ti3+, while elevated sintering temperatures further enhance Ti3+ concentration, attributed to the enhanced lattice activity of TiO2. The increasing TiO2 generated more Al2TiO5 with Al2O3, which accumulated at grain boundaries, inhibiting grain growth through a pinning effect and forming more uniform and smaller grains, thereby enhancing mechanical property. Optimal comprehensive properties were achieved at a sintering temperature of 1500 degrees C with 6 % TiO2 content, demonstrating a density of 3.88 g/cm3, volume resistivity of 1.2 x 1011 Omega cm, dielectric strength of 3.6 x 106 V/m, hardness of 14.4 GPa, and thermal conductivity of 17 W/(m & sdot;K). The series of outstanding performances confirm that Al2O3 ceramic with TiO2 doping is an excellent candidate material in advanced semiconductor processing.

In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this study,continuous carbon fiber reinforced Li2O-Al2O3-SiO2(Cf/LAS)glass ceramic composites doped with SiC particles(SiCp)were prepared by slurry immersion winding and hot pressing sintering.Effect of matrix crystallinity on ablative properties of the composites under ultra-high heat flux was investigated.By utilizing heat absorption and low thermal conductivity characteristics associated with SiO2 gasification within composite materials,both surface and internal temperatures of these materials are effectively reduced,thereby ensuring the safe operation of aircraft and electronic devices.Results indicate that the average linear ablation rate of composites doped with 10％(in mass)of SiCp significantly decreases at a heat flux of 20 MW/m2.Transmission electron microscope observation reveals that the doped glass matrix exhibits increased crystallinity,reduced internal stress,and minimized lattice distortion,thereby enhancing the composites' high-temperature performance.However,excessive SiCp doping leads to reduced crystallinity and deteriorated ablation performance.Ultimately,the average linear ablation rate of Cf/LAS composites with 10％(in mass)SiCp at 20 MW/m2 heat flux is comparable to that of commercial carbon/carbon composites,accompanied by providing lower thermal conductivity and higher bending strength.This novel high-performance Cf/LAS composite is cost-effective,short-cycled,and suitable for mass production,offering promising potential for widespread application in ablation-resistant components of hypersonic vehicles.

The mechanical foaming of Al2O3/C precursors has been recently introduced to solve the problem of uneven N/O content and particle size distribution in the conventional carbothermal reduction nitriding method, but issue of high oxygen content and residual carbon persists. By smashing macroscopic Al2O3/C precursor bricks formed from the mechanical foaming method, AlN powder synthesization conditions, including sintering temperature, holding duration, and nitrogen flow rate, were systemically investigated to remarkably reduce oxygen content. The XRD results indicate that the coexistence of AlN and Al2O3 phases in the powder turns to the full presence of AlN phases when the nitriding temperature is higher than 1575 degrees C for 4 h. As the nitriding temperature increased from 1575 degrees C to 1650 degrees C for 4 h, the particle size of aluminum nitride powder increased, the nitrogen content slightly increased, and the oxygen content obviously decreased. The nitrogen content will rise and the oxygen content diminish when higher holding duration was established. With the increase of nitrogen flow rate, the particle size distribution of the powder becomes more concentrated. Following the optimized sintering conditions of 1600 degrees C for 4 h, AlN particles with oxygen content of 0.584 wt%, nitrogen content of 32.3 wt%, particle size of 0.91 mu m, and specific surface area of 23.8 m2/g were successfully synthesized. Subsequently, the de- carbon procedure was determined by DSC analysis to notably reduce residual carbon content to 580 ppm. Finally, with 4 wt% Y2O3 incorporation, AlN ceramics with thermal conductivity of 194 W/m & sdot;K, bending strength of 350 +/- 50 MPa, and modulus of 220 GPa were yielded, after being sintered at 1800 degrees C for 30 h under pressure-free nitrogen conditions.

The integration, miniaturization, and high frequency of microwave vacuum electronics put forward higher requirements for heat-conducting and wave-absorbing integrated materials. However, these materials must balance the dispersion and isolation of wave-absorbing components to optimize absorption while maintaining the continuity of thermal conductivity pathways with low defect rates and minimal interfaces. This presents a significant challenge in achieving both high thermal conductivity and efficient wave absorption simultaneously. Here, AlN/FeNi microwave-attenuating ceramics were synthesized via non-pressure sintering in a nitrogen atmosphere. The influence of FeNi content (0-20 wt%) on the density, phase composition, microstructure, microwave-absorption properties and thermal conductivity of the composites was investigated. AlN/FeNi composites consist primarily of an AlN phase with FeNi0.0578, Fe, AlYO3, and Al5Y3O12 as secondary phases, and the microstructure is uniform and dense. As the FeNi content rises from 0 to 20 wt%, the density of the composites sintered at 1800 °C × 2 h increases from 3.3 to 3.7 g/cm3. Their X-band (2-18 GHz) dielectric constant goes up from 6.5 to 8.5, the dielectric loss factor rises from 0.1 to 0.9, and thermal conductivity diminishes from 130 to 123 W/m·K. Upon reaching an FeNi content of 20 wt%, the composite achieves a minimum reflection loss of -39.1 dB at 9.5 GHz, with over 90% absorption across an effective absorption bandwidth covering 2.5 GHz. It exhibits excellent impedance matching, electromagnetic wave-attenuation properties, a relative density of 98.6%, and a thermal conductivity of 123 W m-1 K-1. The prepared AlN/FeNi composites, with integrated outstanding microwave-absorption capabilities and thermal conductivity, holds great promise for applications in 5G communications, aerospace, and artificial intelligence.

Unilateral radiating antennas are widely studied due to their ability to provide lateral or unidirectional radiation patterns, which are especially suitable for indoor and office Wi-Fi router applications. In this letter, a unilateral radiating rectangular dielectric resonator antenna (DRA) without a ground plane is proposed. A temperature stable low-loss 0.8MgTiO(3)-0.2Mg(2)SiO(4)-0.06CaTiO(3) (MT-MS-CT) composite ceramic prepared via solid-state reaction and sintered at 1380 degrees C is utilized for the proposed DRA. Notably, the MT-MS-CT composite ceramic shows good dielectric performance with a permittivity of epsilon(r)similar to 13, a quality factor of Qxf(0)similar to 115,000, Q = 1/dielectric loss, f(0) = 8.6 GHz, and a temperature coefficient of resonant frequency TCF similar to+4.6ppm/degrees C. Its unilateral radiation pattern is based on the complementary magnetic dipole and electric dipole, where the excited dominant TE111 mode of the rectangular DRA serves as the magnetic dipole and a probe acts as an electric dipole. The proposed prototype antenna fabricated using the composite ceramic has a unilateral radiation pattern with wide impedance bandwidth, reasonable gain, and radiation efficiency of 95%.

Low-cost amorphous nano-carbon (ANC) was employed as an absorbent to modify the microwave performance of AlN ceramics (AlN-4 wt% Y2O3-x wt% C, x = 0, 2.0, 3.8, 3.9, 4.0) via hot-pressing sintering, and the thermal and mechanical properties were also investigated. With the increase of ANC content from 0 to 4.0 wt%, the relative density of AlN composite decreases from 3.28 g cm(-3) to 3.16 g cm(-3) when sintered at 1800 degrees C for 2 h, and with the increase of sintering temperature from 1700 degrees C, the density of the 4.0 wt% ANC doped AlN composite presents trend of increase and reaches the maximum value of 3.16 g cm(-3) at 1800 degrees C and then decreases. The XRD pattern shows that the composites are composed of AlN and Y-Al-O (YAG, YAP, YAM et al.) phases. SEM results indicate that average grain sizes for AlN and secondary phases gradually decrease with increasing carbon content, suggesting inhibited grain growth due to ANC addition. No obvious changes in phase constitution nor intensity changes were detected with the increase in carbon content and sintering temperature. As the carbon content increases from 0 to 4.0 wt%, the dielectric constant gradually increases from similar to 9 to 13.89 at 10 GHz, the dielectric loss gradually increases from the vicinity of 10(-3) to 0.38 at 10 GHz, and the reflective loss decreases from -27.92 dB to -49.40 dB, the thermal conductivity of the AlN-ANC composite decreases from 116.63 W m(-1) K-1 to 50.13 W m(-1) K-1. In addition, with 4.0 wt% ANC addition, the dielectric constant, dielectric loss, reflective loss, hardness, elastic modulus, bending strength, and fracture toughness are 13.89, 0.38, 49.40 dB, 6.4 +/- 0.4 GPa, 262 GPa, 268.78 MPa, and 1.4 +/- 0.1 MPa m1/2, respectively. Its ability to efficiently absorb microwave energy enhances the performance of devices including radar systems, communication equipment, and microwave heating systems, making it a promising candidate for microwave vacuum electronic applications.

In this paper, the high-quality factor mullite microwave dielectric ceramic is employed to introduce in dielectric resonator antenna (DRA). The microwave dielectric properties of ɛr ∼ 5.8, Q × f ∼ 31 240 at 9.66 GHz, and loss tangent tanδ = 1/Q ∼ 2.7 × 10−4 can be obtained by the solid-state reaction method in mullite microwave dielectric ceramic sintered at 1700 °C. On this basis, the resonant modes of the proposed broadband high-gain rectangular DRA are analyzed by using a dielectric waveguide theoretical model and the antenna performance is evaluated by a commercial CST Microwave Studio 2021® software. It has been found that the proposed rectangular DRA can provide a broad bandwidth of 35.9%, a maximum gain of 10 dBi at 3.61 GHz, and a radiation efficiency of 90% in the range of 3.13–4.42 GHz. For demonstration, adequate consistency between the simulation results and the measurement results was achieved. The proposed DRA has great application potential and value in 5G communication scenarios requiring wideband and high-gain antenna.

Highly transparent Ho:Y2O3 ceramics for laser diode lighting were prepared using the vacuum sintering method with 0.3 at.% Nb2O5 as a sintering additive. The microstructures, transmittance, and luminescence properties of the Ho:Y2O3 ceramic samples were investigated in detail. The transmittance levels of all samples with various Ho3+ concentrations reached ~81.5% (2 mm thick) at 1100 nm. Under the excitation of 363 nm (ultraviolet) or 448 nm (blue) light, Ho:Y2O3 transparent ceramic samples showed that green emission peaked at 550 nm. The emission intensity was strongly affected by the concentration of Ho3+ ions, reaching its highest level in the sample doped with 1 at.% Ho3+. The CIE coordinates of the luminescence were in the green region (i.e., the CIE coordinates of the sample doped with 1 at.% Ho3+ were [0.27, 0.53] and [0.30, 0.69], under the excitation of 363 nm and 448 nm light, respectively). The possibility of its application as laser diode lighting was reported. Under the excitation of 450 nm blue laser, the sample doped with 0.5 at.% Ho3+ had the best performance: the saturated luminous flux, lumen efficiency, and the luminescence saturation power densities were 800 lm, 57.7 lm/W, and 17.6 W/mm2, respectively. Furthermore, the materials have high thermal conductivity and mechanical strength due to their host of rare-earth sesquioxide. Thus, Ho:Y2O3 transparent ceramics are expected to be a promising candidate for green-light-emitting devices for solid-state lighting, such as laser diode lighting.

Y2O3 ceramics is widely used as laser medium or optical window due to its excellent physical and chemical properties and high transparency in wide frequency band of 280 nm-8 mu m. However, preparation of highly transparent Y2O3 ceramics still remains challenge due to its synthetic precursor and nano-powders difficult to meet the requirements. In this work, a spherical monodispersed and submicron-sized Y2O3 powder was prepared by a homogeneous precipitation method using yttrium nitrate and urea as raw materials. Structure, phase evolution and morphology of Y2O3 precursor and the calcined powder were studied by different methods. The synthesized particle precursor exhibits a sphere morphology with diamension around 330 nm, and Y2O3 powder calcined at 800 degrees C for 2 h shows spherical, well-dispersed and uniformed particles with dimension around 260 nm. Based on this spherical Y2O3 powder, transparent Y2O3 ceramics were fabricated by vacuum sintering at 1780 degrees C using 0.3% (in atom) Nb2O5 as sintering additive. The in-line transmittances of Y2O3 ceramics with thickness of 1 mm reach 76.9% at a wavelength of 1100 nm and 65.6% at a wavelength of 400 nm. In conclusion, this study provides a new promising method for preparing Y2O3 transparent ceramics with excellent properties.

Gd2O3-MgO composite ceramics are promising candidates for preparing protective mid-wave infrared (MWIR) windows. However, owing to the different crystal structures of Gd2O3 and MgO after the sintering process, the volume ratio of the two phases must be controlled more precisely to achieve optimum performance. In this study, a nitrate-citrate combustion method was used to prepare Gd2O3-MgO nanopowders with different volume ratios, and composite ceramics were then fabricated via low-temperature pre-sintering and subsequent hot isostatic pressing (HIP). The effect of the Gd2O3:MgO volume ratio on the sintering behaviour, microstructures and optical, thermal and mechanical properties of the composite ceramics was studied in detail. A comprehensive assessment of the above-mentioned properties indicated that the Gd2O3-MgO composite ceramic with a volume ratio of 2:3, which exhibited a transmittance of 80.1-85.8% in the range of 3-5 mu m, thermal conductivity of 17.5 W m(-1) K-1, Vickers hardness of 9.8 GPa and toughness of 1.84 MPa m(1/2), displays the optimum application performance for MWIR windows.

The phase composition, microstructure, electrical and thermal properties of hot-pressed AlN-2 wt% Yb2O3-4 wt% Sm2O3-x wt% TiN (x = 0, 0.4, 0.8, 1, 2, 3, 4) ceramics were systematically investigated. Yb2O3 and Sm2O3 were used to react with Al2O3 in AlN to form Yb3Al5O12, SmAlO3 and SmAl11O18, which made the samples densely sintered. When sintered at higher than 1700 degrees C, the electrical resistivity of AlN ceramics with 2 wt% Yb2O3-4 wt % Sm2O3 decreased significantly to 10(10) Omega.cm. This decrease in resistivity was probably caused by the continuity of the secondary phase, which encasing the AlN grains and deteriorating the thermal conductivity. When sintered at 1650 degrees C, the addition of 0.4-4.0 wt% TiN reduces the electrical resistivity from 8.9 x 10(12) to 2 x 10(10) Omega.cm while maintaining thermal conductivity at around 90 W/m.K with high compactness. Finally, a series of high performance AlN ceramics, with adjustable electrical/thermal properties, could be obtained for modern semiconductor industry.

In this study, Y3-xLaxAl5O12 (0 <= x <= 0.09) ceramics were synthesized, and the phase composition, lattice evolution, and microwave dielectric properties were investigated in detail. Scanning electron microscopy confirms that the addition of moderate amounts of La2O3 improves the grain development of YAG ceramics, but excessive doping destabilizes the crystal structure. Transmission electron microscopy characterization shows that the variation of the dielectric properties of the samples with x-value is related to the occurrence of benign dislocation structures caused by modifications in the type and content of the A-site rare-earth ions. The variations in relative density, dielectric constant, and quality factor remain basically coordinated. The optimum microwave dielectric properties of La3+ doped YAG samples are exhibited as epsilon(r) = 10.61, Q x f = 187, 542 GHz, tau(f) = -31.2 ppm/degrees C when La2O3 is doped at x = 0.015.

A novel composite ceramic, composed of equal-volumetric Zr-stabilized Gd2O3 and MgO phases, was prepared to be transparent in mid-wave infrared range. Zr stabilized Gd2O3 is proved to have a lower lattice parameter (10.7516 angstrom) using XRD refinement. Pressureless sintering behavior of Gd2O3-MgO with/without 2 at% Zr-doping (naming ZGM and GM) was studied via the real-time observation technique. The shrinkage of ZGM green body proceeds steadily up to 1400 degrees C while that of the undoped one shrinks sharply at 1250 degrees C due to Gd2O3 phase transition. The segregation of Zr element along the grain boundaries of Zr-Gd2O3 creates a synergized effect on the grain refinement with pinning effect. Dense ZGM ceramics exhibit superior transmittance of 78.3 %-85.6 % at 3-5 mu m, which show good consistency with the calculated values. The refractive index of Zr- Gd2O3 varies from 1.87 at 3 mu m to 1.80 at 5 mu m, which is smaller than those of monoclinic Gd2O3.