B2O3对BaO-Sm2O3-TiO2微波介质陶瓷性能的影响

为了满足微波器件小型化的需要,开发高介电常数的低温烧结微波介质材料成为一种趋势.采用复合掺杂低熔点氧化物来降低BaO-Sm2O3-TiO2系(BST)微波介质陶瓷的烧结温度,通过X射线衍射和扫描电子显微镜分析其物相组成和显微结构,用阻抗分析仪测量了陶瓷材料的介电性能.结果表明:在Ba4(Sm1-0.15Bi0.15)28/3Ti18O54的基质陶瓷材料中,复合掺杂3%的ZnO和2%的B2O3时,其烧结温度为1060℃,得到的BST微波介质陶瓷的介电性能为:εr≈64,tanδ≈1.2×10-3,τf=-8.3×10-5/℃.     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

(Mg1-xSrx)2Al4Si5O18陶瓷的显微结构与微波介电性能研究

采用固相烧结反应法制备(Mg1-xSrx)2Al4Si5O18陶瓷.Sr掺杂促进低温相β-Mg2Al4Si5O18向高温相α-Mg2Al4Si5O18转变,并拓宽了(Mg1-xSrx)2Al4Si5O18陶瓷的致密化烧结温度范围.X射线衍射结果表明在0≤x<0.2范围内,(Mg1-xSrx)2Al4Si5O18陶瓷以(Mg,Sr)2Al4Si5O18堇青石固溶体形式存在;在0.6相似文献   

(Ba1-xSrx)La4Ti4O15（x=0.8～0.95）陶瓷的微结构及微波介电性能研究

采用固相反应法制备了(Ba1-xSrx)La4Ti4O15(x=0.8~0.95)复合体系微波介质陶瓷,并对其进行物相组成、晶体结构分析以及微波介电性能的研究.研究结果表明,(Ba1-xSrx)La4Ti4O15陶瓷主晶相为SrLa4Ti4O15,并伴随有第二相SrLa8Ti9O15.SEM观察表明,Ba0.2Sr0.8La4Ti4O15陶瓷内部微观结构致密,晶粒尺寸在10~20μm之间,晶界清晰.随着x值逐渐增大,(Ba1-xSrx)La4Ti4O15陶瓷中晶粒形态发生变化,气孔增多.在x=0.8时,(Ba1-xSrx)La4Ti4O15陶瓷具有优良的微波介电性能,即εr=40.86,Q×f≈62806 GHz,τf=20×10 6/℃.随着Ba2+的含量逐渐增加,该陶瓷的介电常数εr单调上升,品质因子Q×f值增加,说明适量的Ba2+替代Sr2+能改善陶瓷的微波介电性能.     

Sb2O3掺杂BNT-BZT1陶瓷的介电和铁电性能

采用固相反应法,制备了[0.9(Bi0.5Na0.5)TiO3-0.1Ba(Ti0.95Zr0.05)O3]+xwt%Sb2O3无铅压电陶瓷,研究了Sb2O3掺杂对样品相结构、介电、铁电性能的影响。实验结果表明:所有样品都形成了纯的钙钛矿结构,无第二相生成。材料存在明显的弛豫现象,从而改善了介电高温温度稳定性(在x=0.6wt%组分、1kHz下、150℃~250℃范围内,介电常数保持在4000左右),但结果同时也表明掺杂使铁电稳定性降低。     

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/℃.     

Ba置换改性(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷结构与微波介电性能的研究

研究了Ba置换改性对Ca [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷微观结构与介电性能的影响.通过XRD与SEM分析发现,当x=0.15,(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3形成了正交晶系钙钛矿结构的单相固溶体;当x=0.20～0.80时,改性陶瓷为正交与六方钙钛矿结构的两相复合固溶体;当x=0.85 时,所形成(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷为六方钙钛矿结构的单相固溶体.(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3系陶瓷微波介电性能的变化与Ba在材料内部的分布状态密切相关,与基材CMNT陶瓷相比:当x=0.15时,陶瓷的介电常数提高,介电损耗降低,谐振频率温度系数向负方向移动:εr=55,Qf值=32000GHz(6.5GHz下),τf=-36.82ppm/℃;当x=0.20～0.80间变化时,(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3两相复合陶瓷的微波介电性能由于复合效应而表现出连续变化的规律:εr= 45～33 ,Qf值= 30500～40200GHz(6.3GHz～7.6GHz下),τf = -17.7～12.52ppm/℃;当x=0.85时,单相钙钛矿固溶体(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3获得良好的微波介电性能:εr=31,Qf值达到44000GHz(8.5GHz下),τf=10.81ppm/℃.     

C（0．）（Li1/2Sm1/2）0．7TiO3微波介质陶瓷的低温烧结研究

采用传统陶瓷制备工艺,制备了掺杂Na2O-CaO-B2O3（NCB）氧化物的C（0．）（Li1/2Sm1/2）0．7TiO3（CLST）陶瓷,研究了NCB掺杂量与晶相组成、显微结构、烧结性能及微波介电性能的关系.研究结果表明：复合氧化物NCB掺杂量在1wt%～15wt%范围内没有杂相生成,晶相仍呈斜方钙钛矿结构.随着NCB添加量的增加,陶瓷致密化温度和饱和体积密度降低,介电常数ε~r、无载品质因数与谐振频率乘积Qf值也呈下降趋势,频率温度系数Tf向正方向增大.NCB氧化物掺杂能有效地将CLST陶瓷的烧结温度由1300℃降低至900℃.添加12.5wt%NCB的CLST陶瓷在低温900℃烧结5h仍具有良好的微波介电性能：εr=73.7,Qf=1583GHz,Tf=140.1&#215;10^-6/℃,满足高介多层微波器件的设计要求.     

BaTi4O9微波介质陶瓷的低温烧结

研究液相多元添加对BaTi4O9微波介质陶瓷的烧结和介电性能的影响.通过添加(CuO和V2O5)烧结助剂来达到降低烧结温度的效果,并且使其保持较好的微波、高频性能.实验结果表明在添加合适的烧结助剂下,烧结温度为1180℃时,BaTi4O9微波介质陶瓷在1MHz下的介电性能ε=41.2,tgδ=5,τ=82×10-6/℃.基本保持了良好的介电性能.     

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。     

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.     

La2O3添加对MgAl2O4-CaAl4O7-CaAl12O19复合材料烧结行为的影响

为适应材料轻量化的发展需要,在1 400~1 600℃温度下开发了MgAl₂O₄-CaAl₄O₇-CaAl₁₂O₁₉（MA-CA₂-CA₆）复合材料,并考察了La₂O₃添加对该复合材料烧结行为、显微结构和力学性能的影响。结果表明,La₂O₃添加剂优先固溶到MA-CA₂-CA₆复合材料组成晶相CA₆中,促使CA₆相发生晶格畸变,有效抑制了CA₆晶粒沿基面的异常长大,其形貌由片状向等轴状趋势转变,促使MA-CA₂-CA₆复合材料制备过程中由于CA₆晶粒异常长大而导致的多孔网状显微结构得以有效消除,因此也极大地改善了Mg²⁺的扩散条件,在一定程度上间接促进了MA晶粒的发育,有效促进了MA-CA₂-CA₆复合材料的烧结。经1 200℃预烧、1 600℃保温2 h烧成后,当La₂O₃的添加量为4wt%时,MA-CA₂-CA₆复合材料试样的显气孔率由19.2%下降至6.1%,体积密度由2.78 g/cm³上升至3.18 g/cm³,制得了MA、CA₂、CA₆晶相呈现交织分布、显微结构致密、有利于其力学性能改善的La₂O₃/MA-CA₂-CA₆复合材料,经1 200℃预烧、-1 600℃保温2 h烧成后的4wt% La₂O₃添加试样,其冷态抗压强度由317 MPa增加到了501 MPa。     

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.     

纳米Fe3O4及Fe3O4-SrFe12O19吸波复合材料的制备及性能

采用共沉淀法成功制备出具有超顺磁性的纳米Fe₃O₄, 并将Fe₃O₄与SrFe₁₂O₁₉复合制成复合吸波材料Fe₃O₄-SrFe₁₂O₁₉, 利用X射线衍射仪(XRD)、透射电镜(TEM)、振动样品磁强计(VSM)和矢量网络分析仪(PNA)对产物的物相、显微结构、磁性能和吸波性能进行了表征与分析。结果表明, 当Fe₃O₄与SrFe₁₂O₁₉质量比为1∶0.3时, Fe₃O₄-SrFe₁₂O₁₉饱和磁化强度为11.1 emu·g^-1, 矫顽力0.86 Oe, 剩余磁化强度0.08 emu·g^-1, 其吸波性能最佳, 最大吸收峰值为-17.7 dB,-5 dB频宽为1.3 GHz, 较Fe₃O₄和 SrFe₁₂O₁₉的最大吸收峰值分别提高247%和185%, 频带分别拓宽1.12 GHz和0.40 GHz。     

CoAl2O4/Al2O3纳米复合陶瓷的结构与表征

利用溶胶-凝胶方法制备了的CoAl2O4/Al2O3纳米复合陶瓷,并用X-ray分析(XRD)、红外光谱(IR)和扫描电镜分析(SEM)对其结构进行了分析.结果表明,随Al2O3含量增多,CoAl2O4尖晶石相从CoAl2O4/Al2O3凝胶中的析晶温度升高.SEM形貌也说明,随Al2O3含量增多,CoAl2O4/Al2O3陶瓷中形成一定的层状结构.     

Highly stable nonlinear behavior against impulse current of ZnO-Pr6O11-CoO-Cr2O3-Y2O3 varistors

The nonlinear electrical behavior against the impulse stress (400-1200 A) in the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃ varistors has been investigated with sintering time. The sintering time did have a significant effect on the clamp ratio, which exhibits a surge protection capability. The varistors sintered for 1 h exhibited the best clamp characteristics, in which the clamp voltage ratio was in the range of K = 1.61-1.92 at a lower impulse current region (5-50 A) and was in the range of K = 2.06-2.55 at a higher single impulse current region (400-1200 A). The best electrical stability against the multi-impulse aging stress of 1200 A was also obtained from the varistors sintered for 2 h, where %ΔE_{1 mA} =−1.6%, %Δα =1.3%, and %ΔJ_L =−4.9%.     

Structural studies of Fe2O3-Bi2O3-CdO glass system

xFe₂O₃·(100 − x)[Bi₂O₃·CdO] system with 0 ≤ x ≤ 50 mol% was prepared and investigated by X-ray diffraction, density, FT-IR and Raman spectroscopies. The XRD patterns confirm the formation of a vitreous structure for x < 35 mol% Fe₂O₃. The evolution of density and molar volume with the addition and increasing of iron content indicates structural changes in the structure of Bi₂O₃·CdO glass matrix. The FT-IR spectrum of the glass matrix reveals a structure realized from BiO₃ pyramidal and BiO₆ octahedral units. With the addition of iron the structure proposed by the glass matrix is changing by the appearance of FeO₄ units. Also the existence of FeO₆ units cannot be excluded. The Raman spectra suggest a structure build from BiO₆ octahedral units. By Raman scattering the presence of structural units characteristic to Fe₂O₃ was not directly observed but the evolution of the spectra is dependent of the iron content.     

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.     

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.