查找使用阿拉丁产品的科研文献

Enhanced negative thermal expansion property in (KMg)xSc2-x(WO4)3 ceramics synthesized by solid–state reaction

Zhiping Zhang,Yuenan Wang,Yang Lei,Fang Zhang,Xiaobing Chen,Hongfei Liu

Negative thermally expanded (NTE) (KMg) x Sc 2-x (WO 4 ) 3 (0 = x ≤ 1.5) ceramics have been prepared via solid-state reaction. X-ray diffraction (XRD) analysis reveals that (KMg) x Sc 2-x (WO 4 ) 3 undergoes a composition-induced phase transition as the (KMg) 3+ -substitution content increases. For x = 0.25, both hexagonal (KMg) x Sc 2-x (WO 4 ) 3 and orthorhombic Sc 2 (WO 4 ) 3 coexisted in the sample. For 0.25 < x ≤ 1, a single-phase, hexagonal (KMg) x Sc 2-x (WO 4 ) 3 , was obtained. When x is further increased to 1.25, monoclinic MgWO 4 impurity was detected in the sample. Meanwhile, as x increases, the grain size of (KMg) x Sc 2-x (WO 4 ) 3 ceramics grows up. Hexagonal (KMg) x Sc 2-x (WO 4 ) 3 ceramics show high densification and strong NTE property. Thermomechanical analysis indicates that the linear coefficients of thermal expansion (CTEs) of hexagonal (KMg) x Sc 2-x (WO 4 ) 3 ceramics decrease from −7.48 × 10 −6  °C −1 to −14.06 × 10 −6  °C −1 with the increase of x. High-temperature XRD analysis reveals that hexagonal (KMg) 0.5 Sc 1.5 (WO 4 ) 3 show an anisotropic NTE. The intrinsic linear CTEs are α a  = α b  = −6.74 × 10 −6  °C −1 , α c  = 11.03 × 10 −6  °C −1 and the volumetric CTE is α v  = −2.52 × 10 −6  °C −1 .

Enhanced thermoelectric properties of Bi2Sr2Co2Oy ceramics by dispersing B2O3 additive

Xu Yingying,Xia Siyi,Zhang Yingjiu,Song Hongzhang,Liu Shaohui,Hao Haoshan

In this study, ceramic samples of Bi 2 Sr 2 Co 2 O y  +  v wt% B 2 O 3 ( v  = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using the solid state reaction method, and the influence of B 2 O 3 additive on their microstructure and thermoelectric properties were investigated. On one hand, the B 2 O 3 additive acted as a sintering aid, enhancing carrier mobility. On the other hand, B 2 O 3 dispersion served as a nano-second-phase, increasing hetero-interfaces and strengthen phonon scattering, thereby effectively suppressing lattice thermal conductivity. By dual optimization of both electric and thermal transport performance, the Bi 2 Sr 2 Co 2 O y  + 0.3 wt% B 2 O 3 sample achieved a high ZT value (thermoelectric figure of merit) of 0.31 at 923 K, which was improved by approximately 33% compared with the pristine Bi 2 Sr 2 Co 2 O y sample.

Investigation on the microcrcaks strengthening effect in the damage behavior of Al2TiO5 flexible ceramics based on the AE

Qingliang Shan,Qian Ma,Changrong Chen,Qiankun Xu,Yudong Xue,Hao Xiong,Yewei Wang,Yuqian Zhou,Anze Shui

In this study, the effect of microcrcaks strengthening on damage evolution of Al 2 TiO 5 (AT) flexible ceramics was investigated by acoustic emission (AE). Results reveal that with increasing content of ZrO 2 , the strength of AT flexible ceramics improves gradually and the strain increases at first then decreases. When the content of ZrO 2 is 12% and 8%, the strength and strain at maximum stress are increased by 154.92% and 38.27%, respectively. In addition, thanks to the “strengthening effect” of ZrTiO 4 on grain boundary microcracks, the damage development thresholds ( σ min and σ onset ), elastic modulus and fracture toughness of AT flexible ceramics modified with ZrO 2 are significantly improved. Moreover, the visible transverse cracks and matrix shedding in ATZ-0 are the most, but the cumulative AE damage events in ATZ-8 and ATZ-4 are more than ATZ-0 at late stage, for which the fracture of ZrTiO 4 glass phase and crack branching induced by ZrTiO 4 should be responsible.

Vacancy engineering for high tetragonal BaTiO3 synthesized by solid-state approaches

Huifeng Xu,Pengfei Wang,Saiwei Luan,Lixia Cheng,Zhenxiao Fu,Xiuhua Cao,Lei Zhang,Shuhui Yu,Rong Sun

Conventionally, tetragonality in BaTiO 3 powder is attributed to grain size, disregarding the role of Ba/Ti ratio. However, our study reveals a significant impact of Ba/Ti ratio on tetragonality in BaTiO 3 . With an increase in Ba/Ti ratio from 0.990 to 1.010, particle size remains around 200 nm. Tetragonality initially rises from 1.006 to a maximum of 1.0092 at Ba/Ti = 1.000, then decreases to 1.005. Lower tetragonality is associated with Ba or Ti vacancies, using density functional theory (DFT), we analyzed the electron density and lattice distinction in BaTiO 3 powders. Both Ba and Ti vacancies affect lattice distortion, the Ti vacancies leading to more significant lattice expansion and lower tetragonality than Ba vacancies. Using this powder, we fabricated high-density BaTiO 3 ceramics and multi-layer ceramics capacitors (MLCCs) with X7R temperature stability (−55 to 125 °C, ±15% coefficient) and excellent reliability. This strategy has broad implications for tetragonal BaTiO 3 nanopowders and MLCCs development.

Fabrication of high-sensitivity Bi0.2-xCexSr0.5La0.3TiO3 (0

Enhanced optical properties and laser performance of Yb:LuScO3 transparent ceramics fabricated with ZrO(NO3)2

Fangliang Shen,Bingheng Sun,Tao Feng,Conghui Huang,Yin Hang,Benxue Jiang,Long Zhang,Jintai Fan

This work aims to fabricate the Yb:LuScO 3 sesquioxides transparent ceramics for use in ultrafast and ultrashort laser technology. 1 at.% Yb:LuScO 3 nanopowders were fabricated using the glycine-nitrate process. ZrO(NO 3 ) 2 was selected as the precursor of ZrO 2 which functions as a sintering aid. Yb:LuScO 3 transparent ceramics with different ZrO 2 content were fabricated by vacuum sintering at 1780 °C and HIPing at 1650 °C, among which the ceramic with 7 at.% ZrO 2 showed the highest transmittance, reaching 81 % at 2000 nm. The ceramic achieved a maximum output power of 1.5 W at 1038 nm with a slope efficiency of 34.8 % and tunable wavelength range exceeding 22 nm. The results demonstrated that Yb:LuScO 3 transparent ceramics can be considered as promising materials in 1 μm solid-state laser applications.

Crystal structure and microwave dielectric properties in CoO-SnO2-Nb2O5 system

Yun Zhang,Shihua Ding,Tianxiu Song,Yingchun Zhang

CoSnNb 2 O 8 ceramic with medium-permittivity was initially generated. Compositionally induced phase formation was identified by X-ray diffraction. Tetragonal rutile-type CoSnNb 2 O 8 was obtained from the reaction of SnO 2 with intermediate phase CoNb 2 O 6 . Both the dielectric constant ε r and quality factor Q  ×  f initially increased with the sintering temperature, reaching the maxima at around 1225 °C, and declined thereafter. They were discussed based on the ionic polarizabilities and packing fraction, respectively. The temperature coefficient of resonant frequency τ f primarily depended on the Nb-site bond valence, as well as oxygen octahedra distortion. When sintered at 1225 °C, the CoSnNb 2 O 8 ceramic exhibited optimum properties with ε r  = 31.8, Q  ×  f  = 43,000 GHz, and τ f  = 35.01 ppm/°C.

Effect of R2O3 (R=Y, La) on the microstructure, optical, and photoluminescent properties of MgAl2O4:Cr3+ transparent ceramics

Yibo Zhang,Shen Wang,Biao Liu,Yan Hao

MgAl 2 O 4 :Cr 3+ transparent ceramics were prepared by a hot-pressed sintering process with Y 2 O 3 and La 2 O 3 as sintering aids, and the effects on the microstructure, densification, optical transmission, and photoluminescent properties were investigated. The sintering aids of Y 2 O 3 and La 2 O 3 enhanced the relative density, reaching 99.33% with 2.4 wt% Y 2 O 3 and 99.24% with 0.8 wt% La 2 O 3 . La 2 O 3 also inhibited abnormal grain growth and obtained ceramics with uniform grain size. In addition, the optical transmission was also improved with Y 2 O 3 and La 2 O 3 as sintering aids. The transmission of the ceramic with 2.4 wt% Y 2 O 3 exceeded 78% in the region of 700–6000 nm and reached 83% at 1450 nm. Moreover, Y 2 O 3 and La 2 O 3 both contributed to improving the quantum yield of the ceramics, especially for Y 2 O 3 , and the quantum yield was about 0.354, which was approximately two times higher than that without R 2 O 3 . In summary, La 2 O 3 was helpful for improving sintering process, inhibiting grain growth, and homogenizing the grain size, while Y 2 O 3 was significant for enhancing the optical and photoluminescent properties.

Ni metal coating boosting the thermoelectric performance of In2O3(ZnO)5 ceramics

Jun Guo,Peng Qin,Zheng Ma,Qiong-Lian Yang,Jing Feng,Zhen-Hua Ge

A new approach was developed for enhancing the thermoelectric performance of In 2 O 3 (ZnO) 5 ceramics. Ni coating layer on the surface of In 2 O 3 (ZnO) 5 powders was prepared by chemical plating. The Ni-Coated In 2 O 3 (ZnO) 5 powders was densified to composite bulk with Ni enrichment in the grain boundaries. The composite sample obtained a remarkably enhanced dimensionless thermoelectric figure of merit (ZT) of 0.39 at 973   K, which is 3.6 times higher than that of a pristine In 2 O 3 (ZnO) 5 sample.

Influence of phosphorus sources on lithium ion conducting performance in the system of Li2O–Al2O3–GeO2–P2O5 glass–ceramics

Jing Yang,Zhen Huang,Bingxin Huang,Jing Zhou,Xiaoxiong Xu

NASICON-type structure lithium ion conductors have been considered as promising solid electrolytes due to its very high Li + -ion conductivity and chemical stability. In this paper, NASICON-type structured Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) glass–ceramics are prepared from crystallization of glass powders, which are obtained by a simple melt-quench method. NH 4 H 2 PO 4 , H 3 PO 4 , P 2 O 5 and H 3 PO 4 &Al(PO 3 ) 3 are used as phosphorus sources, respectively. The obtained LAGP glass–ceramics are systematically characterized with X-ray diffraction, field emission scanning electron microscopy , differential scanning calorimetry and AC impedance spectroscopy . The different impurities are formed depending on the phosphorus sources, which further influence the microstructure. As a result, the lithium ion conductivity is significantly affected by the phosphorus sources. The highest conductivity of 5.21   ×   10 −   4   S·cm −   1 is obtained when H 3 PO 4 is used as the phosphorus source under optimum conditions.

Fabrication and characterization of porous CaSiO3 ceramics

Yue Hu,Zhen Xiao,Huanping Wang,Can Ye,Yuqian Wu,Shiqing Xu

Porous CaSiO 3 ceramics were prepared via a solid-state reaction method using CaCO 3 and SiO 2 as raw materials and active carbon as a pore-forming agent. The results indicated that porous CaSiO 3 ceramics could be obtained under a low sintering temperature of 1320 °C. The addition of active carbon significantly affected the volume density, microstructure, pore size distribution and mechanical strength of porous CaSiO 3 ceramics. With the increase of active carbon content, the volume density decreased, meanwhile the pore size and porosity increased gradually. Besides, the three-point bending tests demonstrated that the mechanical strength was decreased with increasing active carbon content. However, all the porous ceramics still exhibited high mechanical strength. These results implied that the increase of active carbon content not only enlarged the pore size and enhanced the porosity, but also kept a remarkable mechanical strength of porous CaSiO 3 ceramics. Therefore, these rationally designed CaSiO 3 porous ceramics will be a highly potential material in various applications due to its high mechanical strength, low sintering temperature and narrow pore size distribution.

Fine-grained ZnO ceramic fabricated by high-pressure cold sintering

Yang Shi,Zhangyi Huang,Jingjing Chen,Mao Deng,Mingyu Su,Jianqi Qi,Jun Wang,Haomin Wang

High-density (∼99.34%), fine-grained (∼685 nm) ZnO ceramic was successfully fabricated by the high-pressure cold sintering. The influences of solvent (liquid phase) fraction and the applied pressure on densification in this process have been carefully studied. The excess solvent can result in grain refinement, but impedes the densification of ceramic. Significantly, the role of pressure is unlike that in the traditional pressure-assisted sintering, which can improve the densification and inhibit grain growth. There is a critical pressure (∼1 GPa) that can be associated with the transition of recrystallization from heterogeneous nucleation to homogeneous nucleation . When the pressure is lower than this critical value, the applied pressure can improve densification, but cannot inhibit grain growth. Above the critical value, the densification is dramatically weakened and many small crystals in the interstitial space between grains can be found.