ZnCr2O4-V2O5-Li2O-ZnO湿敏材料的气体选择性研究

测试了ZnCr2O4-V2O5-Li2O-ZnO感湿体在H2、CO2、煤气、酒精蒸汽等气体环境中电阻的变化情况.结果表明,电阻值明显随环境温度变化但基本不受气体影响.     

Bi2O3掺杂对Mg4Nb2O9陶瓷的微结构及微波介电性能的影响

采用固相反应法制备了Mg4Nb2O9基微波介质陶瓷,研究了Bi2O3掺杂对Mg4Nb2O9陶瓷烧结行为、相结构、显微结构及微波介电性能的影响。实验结果表明:Mg4Nb2O9陶瓷烧结温度随Bi2O3掺杂量的增加而减小,添加2.0wt%Bi2O3,烧结温度从1350℃降低至1175℃;随Bi2O3添加量从0.0wt%增大到3.0wt%,最强峰(104)晶面间距d值由2.756nm增大至2.769nm;Mg4Nb2O9陶瓷的微波介电性能随Bi2O3掺杂量增加而变化;掺杂2.0wt%Bi2O3的Mg4Nb2O9陶瓷在1175℃保温2小时烧结,获得亚微米级陶瓷,且具有最佳的微波介电性能,εr为12.58,Q×f为71949.74GHz。     

添加剂对Y2Ti2O7陶瓷的微波介电性能的影响（英文）

研究了CrO3、Nb2O5、SiO2及Al2O3对Y2Ti2O7陶瓷的烧结性能、相组成和微波介电性能的影响.其中Nb2O5掺杂能够降低Y2Ti2O7陶瓷材料的烧结温度,提高基体陶瓷的介电常数和品质因子,引起谐振频率温度系数的明显变化.且随着Nb2O5含量的增多,所有样品的主晶相仍为立方烧绿石型Y2Ti2O7,Nb5+可能进入烧绿石结构中,部分取代Ti4+所在位置.实验结果表明:1mol%Nb2O5掺杂的陶瓷材料在1420℃下烧结致密,具有最佳的微波介电性能:εr=61.8,Q×f=9096GHz(f=5.494GHz),τf=54×10-6/℃.     

Sc2O3-Y2O3-ZrO2陶瓷材料热物理性能

采用固相合成法制备了6.3%Sc_2O_3-1.3%Y2O3-92.4%ZrO_2(摩尔分数)陶瓷材料。分别利用X射线衍射、示差扫描量热法、高温热膨胀仪和激光导热法对陶瓷材料的物相组成、高温相稳定性、热膨胀系数和热扩散等性能进行了表征。结果表明,经1600℃烧结6h,该陶瓷材料由单一的立方相结构组成,具有良好的高温相稳定性,热导率低于传统的6~8YSZ,是一种良好的热障涂层候选材料。     

Li2CO3-B2O3-V2O5掺杂ZnO-TiO2陶瓷低温烧结的研究

以Li2CO3、B2O3和V2O53种常见的低熔点氧化物为烧结助剂,用传统固相法制备了Li2CO3-B2O3-V2O5掺杂的ZnO-TiO2微波介质陶瓷,并利用XRD、SEM等研究了ZnO-TiO2陶瓷的烧结行为、物相组成、显微结构特征及微波介电性能等。结果表明,当掺入3%(质量分数)Li2CO3-B2O3-V2O5时,在840℃烧结2h可制备出体积密度为4.99g/cm3的ZnO-TiO2陶瓷,达到理论密度的96.5%以上,εr、Q.f、τf分别约为24、22900GHz、-4×10-6/℃。     

Bi2O3掺量对Li0.45Ni0.2Ti0.1Fe2.25O4铁氧体显微结构及磁性能的影响

采用氧化物法陶瓷工艺,在缺铁配方的基础上,制备不同Bi2O3掺量的Li0.45Ni0.2Ti0.1Fe2.25-δO4(δ=0.06)铁氧体样品。结果表明,添加Bi2O3没有在锂铁氧体中形成杂相,烧结后陶瓷样品物相组成单一,结晶状况良好;适量的Bi2O3能有效改善材料微观形貌,促进锂铁氧体的烧结致密化,有助于提高材料的饱和磁化强度4πMs和剩磁比R,降低矫顽力Hc。Bi2O3掺量为1.5%(质量分数)的样品具有较好的综合性能,表观密度d为4.72g/cm3,饱和磁化强度4πMs为2.3T,剩磁比R为0.853,矫顽力Hc为2.3×102 A/m。     

双相质子导体BaCe0.9Y0.1O3-δ/La1.95Ca0.05Ce2O7-δ的制备及性能研究

采用固相反应法成功制备了双相质子导体BaCe0.9Y0.1O3-δ/La1.95Ca0.05Ce2O7-δ(7∶3、6∶4、5∶5、4∶6、3∶7)。用X射线衍射仪、扫描电子显微镜分别对样品的物相结构、微观形貌进行了表征,对样品在CO2和沸水中的稳定性进行了研究,并应用IM6e型电化学工作站测定了其在空气、氩气、湿润的4%H2/Ar 3种气氛从450～850℃的电导率。实验结果表明,不同比例复合的样品经1500℃烧结后均形成了明显的双相结构且获得了致密的烧结体。随着样品中La1.95Ca0.05Ce2O7-δ比例的增加,其对CO2和沸水的化学稳定性增加。在所研究的各种比例的复合材料中,BaCe0.9Y0.1O3-δ-La1.95Ca0.05Ce2O7-δ(3∶7)具有最高的电导率,850℃时在湿润的4%H2/Ar气氛下的电导率为2.49×10-2S/cm,电导活化能为1.13eV。     

炭黑包覆Al2O3掺杂LiMn2O4正极材料的研究

使用醋酸锂、醋酸锰和氧化铝为原料,采用高温固相法合成掺杂Al离子的LiMn2O4二级产物。合成化学计量比为n(Li)∶n(Mn)∶n(Al)=1.3∶1.9∶0.1。首次烧结温度450℃,烧结时间4h;二次烧结温度750℃,煅烧时间为40h。合成样品采用XRD进行材料表征。测试结果表明:合成样品为尖晶石结构,结晶度较高。所得样品使用炭黑包覆处理,并制成实验性电池,对其进行交流阻抗测试(EIS)分析、循环伏安特性(CV)测试、充放电及循环性能测试分析。实验结果表明:包覆后的正极材料改善了LiMn2O4的大电流充放电性能,该材料在0.5C的首次放电比容量为93mAh/g;包覆材料增强了在大电流充放电下的容量保持率,极大地改善了电池的循环性能,该材料在充放电倍率为0.2C时,32次循环后的容量保持率为92.5%。     

ZnO-Nb2O5掺杂SnO2基陶瓷研究

通过常压烧结制备SnO2基陶瓷,研究了ZnO、Nb2O5单掺杂及ZnO-Nb2O5复合掺杂对SnO2基陶瓷的烧结性能及电阻率的影响。采用SEM及XRD对试样分别进行了微观结构观察及物相分析。研究表明,掺杂ZnO能提高陶瓷的体积密度,但对于降低电阻率的影响不明显,当ZnO掺杂量在0.5%～0.75%(质量分数)时,SnO2基体积密度可达到6.67～6.73g/cm3;掺杂Nb2O5不能有效提高烧成陶瓷的体积密度,但能显著降低SnO2基陶瓷的电阻率;0.5%(质量分数)ZnO～1.5%(质量分数)Nb2O5复合掺杂在1450℃下烧成的陶瓷可得到较好的性能,其体积密度可达到6.61g/cm3,常温电阻率为867.84Ω.cm。     

正交试验法优化长余辉发光材料Sr2MgSi2O7∶Eu2+,Dy3+的合成工艺

采用高温固相法在碳粉还原气氛下合成蓝色长余辉发光材料Sr2MgSi2O7∶Eu2+,Dy3+。通过正交试验,以初始余辉亮度和余辉时间为评价指标,研究了烧结温度、Eu2+、Dy3+和硼酸的摩尔分数对发光材料余辉性能的影响。结果表明:各个因素在实验设定水平范围变化时,最佳合成工艺为烧结温度1300℃,Eu2+、Dy3+和硼酸的摩尔分数分别为2%,4%,10%。按照上述工艺条件合成的样品余辉性能最佳,初始余辉亮度可达2238mcd/m2,余辉时间超过1400s。样品具有250nm～450nm的激发范围,发射峰位于470nm。     

Varistor properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics

The varistor properties of the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃-In₂O₃ ceramics were investigated for different concentrations of In₂O₃. The increase of In₂O₃ concentration slightly increased the sintered density (5.60-5.63 g/cm³) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In₂O₃. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In₂O₃ acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 10¹⁷ to 0.24 × 10¹⁷/cm³ with increasing concentration of In₂O₃.     

Nanocrystallization of SrBi2Nb2O9 from glasses in the system Li2B4O7---SrO---Bi2O3---Nb2O5

Transparent glasses in the system (100−x)Li₂B₄O₇–x(SrO---Bi₂O₃---Nb₂O₅) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi₂Nb₂O₉ (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (_r) and the loss factor (D) for the lithium borate, Li₂B₄O₇ (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix.     

Phase relations of the Li2O-Ta2O5-B2O3 and Li2O-WO3-B2O3 systems and promising nonlinear optical compounds in K2O-Ta2O5-B2O3 system

The subsolidus phase equilibria of the Li₂O-Ta₂O₅-B₂O₃, K₂O-Ta₂O₅-B₂O₃ and Li₂O-WO₃-B₂O₃ systems have been investigated mainly by means of the powder X-ray diffraction method. Two ternary compounds, KTaB₂O₆ and K₃Ta₃B₂O₁₂ were confirmed in the system K₂O-Ta₂O₅-B₂O₃. Crystal structure of compound KTaB₂O₆ has been refined from X-ray powder diffraction data using the Rietveld method. The compound crystallizes in the orthorhombic, space group Pmn2₁ (No. 31), with lattice parameters a = 7.3253(4) Å, b = 3.8402(2) Å, c = 9.3040(5) Å, z = 2 and D_calc = 4.283 g/cm³. The powder second harmonic generation (SHG) coefficients of KTaB₂O₆ and K₃Ta₃B₂O₁₂ were five times and two times as large as that of KH₂PO₄ (KDP), respectively.     

Les phases SrLa2Al2O7 et SrGd2Al2O7

SrLa₂Al₂O₇ and SrGd₂Al₂O₇ belong to the structural type Sr₃Ti₂O₇. In SrGd₂Al₂O₇ strontium and gadolinium occupy respectively the 12 and 9 coordinated sites, whereas in SrLa₂Al₂O₇ the homologous cations are statistically distributed. The fluorescence spectra of both phases activated by Eu³⁺ ions show that the only possible position of Eu³⁺ is the 9 coordinated site.     

Refractories based on 3Er2O3-Ta2O5

Refractory Er₂O₃-Ta₂O₅ compositions in the high Er₂O₃ region were prepared by coprecipitation as hydroxides, followed by calcination. Based on x-ray diffraction and wet chemical and electron microanalysis, the fluorite phase was found at 17.3–34.2 (±0.5) mole percent Ta₂O₅. This fluorite phase was stable to at least 2140 C in reducing atmospheres; although measurable vaporization occurred above 1975 C. Above 2100 C minor Ta reduction with preferential vaporization of Er and O was observed.     

Bi2O3助熔剂对CaO-B2O3-SiO2/Al2O3玻璃陶瓷复合材料性能的影响

以CaO-B₂O₃-SiO₂(CBS)玻璃粉体和Al₂O₃陶瓷粉体为原料,通过在CBS与Al₂O₃的质量比固定为50:50的玻璃-陶瓷复合材料中添加适量的Bi₂O₃作为烧结助熔剂,探讨了Bi₂O₃助熔剂对CBS/Al₂O₃复合材料的烧结性能、介电性能、抗弯强度和热膨胀系数的影响规律.研究表明:Bi₂O₃助熔剂能通过降低CBS玻璃的转变温度和黏度促进CBS/Al₂O₃复合材料的致密化进程,于880 ℃下烧结即能获得结构较致密、气孔较少的CBS/Al₂O₃复合材料.然而,过量添加Bi₂O₃将使玻璃的黏度过低,从而恶化CBS/Al₂O₃复合材料的烧结性能、介电性能及抗弯强度.当Bi₂O₃的添加量为CBS/Al₂O₃复合材料的1.5wt%时,于880 ℃下烧结即能获得最为致密的CBS/Al₂O₃复合材料,密度为2.82 g·cm^-3,这一材料具有良好的介电性能(介电常数为7.21,介电损耗为1.06×10^-3),抗弯强度为190.34 MPa,0~300 ℃的热膨胀系数为3.52×10^-6 K^-1.     

Properties and Structures of Bi2O3-B2O3-TeO2 Glass

Glass formation range of Bi₂O₃—B₂O₃—TeO₂ system has been investigated（B₂O₃ < 40 mol%）.Four glasses with compositions xBi₂O₃—3OB₂O₃—（70—x）TeO₂（x = 40,50,60 and 70 mol%） have been prepared by using melt quenching technique.The effect of Bi₂O₃ content on thermal stability,optical properties and structures of these four Bi₂O₃—B₂O₃—TeO₂ glasses is systematically investigated by inductive coupled plasma emission spectrometer（ICP）,differential scanning calorimetry（DSC）,Raman spectra and X-ray photoelectron spectroscopy（XPS）.It is found that the density,refractive index and optical basicity increase with increasing Bi₂O₃.The Raman spectra and XPS spectra show that the glass network is mainly constituted by the[BiO₆] octahedron,[TeO₄]trigonal bipyramidal,[TeO₃]trigonal pyramid,[BO₃]trigonal pyramid and[BO₄]tetrahedron structural units.With increasing Bi₂O₃,the coordination number around B atom changes from 3 to 4 and [TeO₄]units are converted to[TeO₃]units.Bi⁵⁺ ions may exist in Bi₂O₃—B₂O₃—TeO₂（BBT） system and their amount grows with increasing Bi₂O₃ content.     

The vibrational spectra of the intermediate compounds in the system Y2O3P2O5 and Gd2O3P2O5

The Infrared- and Raman-spectra of the intermediate compounds were studied for clues to their structural behavior as related to luminescence response. It was found that the degree of polymerization of PO₄ polyhedra increases in the phosphate-rich region and perhaps in the RE-oxide-rich region as well which was evident from the shift of stretching bands towards the higher energy side. Except in orthophosphates, the PO₄ polyhedra occupy more than one non-equivalent lattice site in all the phosphates.     

Observation of broadband infrared luminescence in a novel Bi-doped P2O5-B2O3-Al2O3 glass

A novel Bi-doped P₂O₅-B₂O₃-Al₂O₃ glass was investigated, and strong broadband NIR (near infrared) luminescence was observed when the sample was excited by 445 nm, 532 nm, 808 nm and 980 nm lasers, respectively. The max FWHM with 312 nm, the lifetime with 580 μs and the σ_emτ product with 5.3 × 10^− 24 cm² s were obtained which indicates that this glass is a promising material for broadband optical amplifier and tunable laser. The effect of the introduction of B₂O₃ on the glass structure and Bi-ions illuminant mechanism were discussed and analyzed. It is suggested that the introduction of B₂O₃ makes the glass structure closer, and the broadband NIR emission derives from Bi⁰:²D_3/2 → ⁴S_3/2 and Bi⁺:³P₁ → ³P₀ transitions.     

High-pressure modifications of CaAl2O4 and CaGa2O4

The modifications of CaAl₂O₄ and CaGa₂O₄ with the stuffed tridymite structure were examined under high temperatures (600 ～ 1500 °C) and high pressures (10 ～ 40 kb). Calcium monoaluminate CaAl₂O₄ was found to transform to three kinds of high-pressure modifications. The original CaAl₂O₄ (CA-I) changed to the phase CA-II which had m-CaGa₂O₄ type structure with a different array of tetrahedra in the six-membered rings of tetrahedron. The phase CA-II transformed either to the phase CA-IV with CaFe₂O₄ type structure or to an unknown phase (CA-III) under high pressures. The phase CA-IV was obtained under the pressures above 30 kb and at the temperatures above 1000 °C. Calcium monogallate CaGa₂O₄ transformed to the CaFe₂O₄ type structure above 30kb and 700 °C. No phases such as CA-II and CA-III were found. The structural relations among these modifications were discussed.