BaTiO3陶瓷中Nb2O5-Zn0.8Mg0.2TiO3的掺杂效应

研究了BaTiO3-Nb2O5-Zn0.8Mg0.2TiO3系统的介电性能及微观性能。SEM和XRD分析发现,在掺杂x(Nb)=1%的BaTiO3陶瓷中,Zn0.8Mg0.2TiO3的固溶度小于4%。Nb2O5和Zn0.8Mg0.2TiO3用量均为1%时,BaTiO3陶瓷为赝立方相结构,当x(Nb)>2%时,陶瓷样品(002)和(200)衍射峰相互分开,研究表明,BaTiO3陶瓷为四方相,且随着Nb用量增加,四方率增强。此外,Nb用量增加还使BaTiO3陶瓷室温介电常数降低,而同时居里点升高。当x(Nb)=2%和x(ZMT)=1%时,在空气中于1 180℃下烧成的BaTiO3陶瓷材料的主要性能指标为:298 K时介电常数2ε98 K=2 004,介电损耗tanδ=0.84%,密度ρ=1.4×1012Ω.cm,-55~ 150℃,电容量温度变化率△C/C≤±15%。     

烧结气氛对X8R陶瓷材料结构与性能的影响

研究了Yb/Mg受主离子协同掺杂对BaTiO3陶瓷材料分别在空气、还原性气氛中,以及热处理过后的结构与性能的影响。X-射线衍射(XRD)分析表明,还原性气氛烧结抑制了受主离子在BaTiO3中的固溶度,使材料出现第二相Yb2Ti2O7。差热扫描热分析(DSC)测量图谱表明,过量的Yb掺杂破坏了陶瓷的壳-芯结构。在不同的气氛烧结条件下,通过适当调整Yb/Mg掺杂量,可获得既适用于Pd/Ag内电极又适用于Ni内电极且满足在-55~ 150℃范围内,容量随温度的变化率满足±15%内(X8R)特性要求的多层陶瓷电容器(MLCC)介质材料。     

气相法对BaTiO3陶瓷扩渗Gd元素及其电性能研究

采用气相法对BaTiO3 陶瓷扩渗Gd元素 ,使BaTiO3 陶瓷的导电性发生了显著变化 ,其室温电阻率从 4 .0× 10 12 Ω·m下降为 2 .76× 10 3 Ω·m ,而且随着频率增大和温度升高 ,交流电导逐渐增大 ,BaTiO3 陶瓷的导电性更强。Gd扩渗后BaTiO3 陶瓷的晶粒电阻随着温度的变化 ,呈现NTCR效应 ,而晶界电阻随着温度的变化 ,呈现PTCR效应 ,且晶界电阻远远大于晶粒电阻 ,说明该材料的PTCR效应是由晶界效应引起的。Gd扩渗使BaTiO3 陶瓷的介电常数显著降低 ,且随频率的增大而逐渐减小 ,介电常数随温度的变化呈PTC效应 ,并使BaTiO3 陶瓷的居里温度升高为 130 .6°C。     

施受主共掺杂对BaTiO3陶瓷介电性能的影响

通过传统的球磨工艺,分别以MnCO3、Co2O3为受主杂质,La2O3、Nb2O5、Bi2(SnO3)3为施主杂质对BaTiO3陶瓷进行掺杂。实验表明,BaTiO3陶瓷介电性能跟施主杂质与受主杂质的比例有关。当施主杂质与受主杂质的比例较大时,介电常数-温度(-εT)曲线趋于平缓,BaTiO3陶瓷呈强铁电弥散性,介电损耗-温度(tan-δT)曲线趋于平滑,介电损耗-频率(tan-δf)曲线呈松弛极化损耗特性。当施主杂质与受主杂质的比例较小时,-εT曲线出现较大的居里峰值,BaTiO3陶瓷呈普通铁电体的性质,tan-δT曲线也出现较大峰值,tan-δf曲线表现为电导损耗特征。BaTiO3陶瓷晶粒的"核-壳结构"模型能较好地解释这一现象。     

稀土掺杂对钛酸钡陶瓷介电性能的影响规律

在BaTiO3(BT)-Nb2O5-ZnO系统中引入硼硅酸盐助烧剂,加入不同稀土氧化物(Y,Nd,Gd,Ho,Yb,Er,Pr,Dy,La,Ce)对BT进行介电性能研究,以期获得中烧X7R陶瓷材料。研究发现,不同稀土氧化物对BT陶瓷电容量温度变化曲线低温峰(约40℃)和高温峰(约127℃)的影响可分为3类。其改性机理可用掺杂后晶粒壳与晶粒芯体积分数的变化来解释。对比上述三种典型的稀土掺杂后BT陶瓷的电镜扫描(SEM)照片得出,不同稀土掺杂BT的室温介电常数与掺杂后BT陶瓷的晶粒生长情况密切相关。     

4ZnO-Bi_2O_3玻璃对Ba_(0.2)Sr_(0.8)Zr_(0.18)Ti_(0.82)O_3陶瓷结构和电学性能的影响

采用溶胶-凝胶法制备Ba0.2Sr0.8Zr0.18Ti0.82O3(BSZT)的粉体,以传统工艺制备了4ZnO-Bi2O3作为添加物的BSZT陶瓷。研究了不同4ZnO-Bi2O3玻璃添加量(质量分数0~3%)对BSZT陶瓷烧结特性、微观结构以及电学性能的影响。结果表明,添加适量的4ZnO-Bi2O3玻璃相,大幅降低了BSZT陶瓷的烧结温度,使得晶粒较小且均匀,无气孔;能提高陶瓷的击穿场强。添加质量分数1%4ZnO-Bi2O3玻璃相的BSZT陶瓷的最优烧结温度较纯BSZT陶瓷降低了350℃,1 k Hz频率下,其相对介电常数约为334、介电损耗约为0.7%;击穿场强为10.2×103 V/mm。     

Bi4Ti3O12掺杂对BST陶瓷性能和结构的影响

研究了Bi4Ti3O12(2%～10%,质量分数)掺杂对(Ba0.71Sr0.29)TiO3(BST)基电容器陶瓷介电常数εr、介质损耗tan δ、容温变化率△C/C等性能及其烧结温度的影响.结果表明,当w(Bi4Ti3O12)=10%时,εr为2 558,tan δ为0.005 0,△C/C=-39.2%,△C/C在25～125℃的范围内比在w(Bi4Ti3O12)=2%时降低了18%,陶瓷的烧结温度降为1 180℃.借助SEM和XRD研究了Bi4Ti3O12掺杂量对样品的显微结构和物相组成的影响,表明Bi4Ti3O12作为烧结助剂包裹晶粒并填充晶粒间形成异相,阻止晶粒生长并细化晶粒.     

低温烧结Ba3Ti5Nb6O28陶瓷及其微波介电性能

研究了CuO助剂对Ba3Ti5Nb6O28陶瓷的烧结特性、微结构以及介电性能的影响。研究表明,适量CuO助剂能使Ba3Ti5Nb6O28陶瓷的烧结温度从1 300℃降到950℃以下。部分CuO会固溶于Ba3Ti5Nb6O28并改变其晶粒形状,出现少量长条状晶粒。随着CuO含量增加,介电常数(rε)无明显变化,品质因数与频率之乘(Q×f)值因固溶物的产生而下降,频率温度系数(τf)向负频率温度系数方向移动。w(CuO)为1%的Ba3Ti5Nb6O28样品,在920℃、2 h下,获得了介电性能较好的低温共烧陶瓷,其介电常数rε为41,Q×f=6 500 GHz,τf=4×10-6/℃。     

Er2O3掺杂对BaTiO3陶瓷介电性能的影响

采用溶胶-凝胶法制备了掺杂Er2O3的BaTiO3陶瓷。测试结果表明,掺杂Er2O3能降低BaTiO3陶瓷的电阻率,且在开始时其电阻率随着掺杂量的增大而升高,在掺杂x(Er2O3)=0.003(摩尔分数)时电阻率最高,然后随掺杂量的升高而降低,在掺杂x(Er2O3)=0.007时电阻率最低,从纯BaTiO3陶瓷的2.6 TΩ.m下降为18 GΩ.m,此变化规律有异于La,Ce,Nd,Sm等稀土元素掺杂的规律。掺杂Er2O3使BaTiO3陶瓷的介电性能发生明显变化,掺杂x(Er2O3)为0.001和0.002时,可改善BaTiO3陶瓷的介电性能和频率特性,具有较好的频率稳定性。掺杂Er2O3使BaTiO3陶瓷的居里温度升高为130.9℃,交流电导随着温度的升高而增大,并在居里温度点附近达到最大。     

稀土氧化物Er_2O_3对钛酸钡基瓷料介电性能的影响

讨论了稀土氧化物Er2O3对BaTiO3基陶瓷系统介电性能的影响。通过掺杂稀土氧化物Er2O3,可使BaTiO3基系统的相对介电常数er保持较高的数值(>3 000);同时,系统的容量温度变化率大为改善,在55~+125℃工作温区内,满足X7R特性;并且随着Er2O3含量的增加,系统的耐压强度也得到了很大的提高,达16 900 V / mm。     

3COM SuperStack 3 Firewall

北京中青联迪科技发展有限公司是团中央直属单位中青高新技术产业发展中心发起组建的高新技术企业,公司是3COM公司防火墙中国区独家总代理。 1.纯硬件设备、采用专业操作系统,高安全性、高性价比,获得国际国内多种认证。 2.操作方便简单,即插即用,全部采用Web图形管理界面,可以在3分钟内完成安装配置。     

一种3×3卷积器的设计

给出了一种基于2的补码的卷积运算算法及其硬件实现体系结构。该算法结构使用了一个特殊的移位累加单元代替并行补码乘法,降低了卷积系数为负数时的计算复杂度。     

InCl分子B^3Ⅱ1态时间分辨谱研究

采用激光诱导荧光技术对InCl分子B3П1→X1∑+荧光光谱进行了分析和归属,并对 B3П1(v′=0)→X1∑+(v″=0)的时间分辨谱进行了观测．首次得到InCl分子B3П1态(v′= 0)无碰撞辐射寿命т0≈353ns,无辐射弛豫速率常数kQ≈1．985×10-10cm3molec-1s-1及 电子跃迁矩｜Re｜2=0．40D2．     

Improved performance of CH3NH3PbI3 based photodetector with a MoO3 interface layer

Planar CH₃NH₃PbI₃ perovskite based photodetectors are fabricated by a facile and low-cost one-step method. The devices show broad spectral photoresponse from the ultraviolet to whole visible region and the performance can be significantly improved by the introduction of a bipolar transporting MoO₃ interface layer between CH₃NH₃PbI₃ film and Au electrode. The photocurrent of the device with an optimized MoO₃ layer is about twice that of the reference device without MoO₃ layer, which results in a high ON/OFF current ratio of 5.9 × 10³ at 5 V. Besides, slightly increased photoresponse speed is also found in the optimized device with rise time and decay time of 21.6 and 9.9 ms, respectively. The improvement can be attributed to the improved hole and electron collection efficiency and the quickly filled in or emptied trap states at the CH₃NH₃PbI₃/Au interface due to the introduction of the bipolar transporting MoO₃ layer.     

Nonlinear Absorption Applications of CH3NH3PbBr3 Perovskite Crystals

Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH₃NH₃PbBr₃ are studied. By exciting the material with a 1044 nm laser, strong two‐photon absorption‐induced photoluminescence in the green spectral region is observed. Using the transmission open‐aperture Z‐scan technique, the values of the two‐photon absorption coefficient are observed to be 8.5 cm GW^?1, which is much higher than that of standard two‐photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO₃), LiTaO₃, KTiOPO₄, and KH₂PO₄. Such a strong two‐photon absorption effect in CH₃NH₃PbBr₃ can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH₃NH₃PbBr₃ are demonstrated, opening new applications for perovskites in nonlinear optics.     

Er3 /Yb3 共掺TeO2-WO3-Bi2O3玻璃的光谱性质

用高温熔融法制备了Er3+/Yb3+共掺的TeO2-WO3-Bi2O3玻璃,研究了该玻璃的吸收和荧光光谱性质.应用Judd-Ofelt(JO)理论计算了Er3+的谱线强度、自发辐射跃迁几率、荧光分支比和辐射寿命等光谱参数,并拟合了相应的强度参数Ωt(t＝2,4,6).Er3+在该玻璃中4I13/2→4I15/2发射的荧光半高宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面为1.03×10-20cm2.其带宽特性FWHM×σpeake乘积优于掺Er3+的硅酸盐、磷酸盐和铋酸盐玻璃,说明这是一种制备宽带光纤放大器的优良基质材料.Er3+在400～850nm波长范围存在着5个上转换发射峰,分别对应Er3+的激发态4I7/2、2H11/2、4S3/2、4F9/2和4I9/2到基态4I15/2的发射,分析了其可能存在的上转换过程.     

Dissymmetrical 3×3 Coupled Optical Accelerometer

Without adding feedback to modulate light path system, the dissymmetrical 3×3 coupled optical accelerometer reduces the complexity of the design of light path system. Experiments prove that it can attain good demodulation effects. As carrier is not needed in this system, the frequency range of input signal is diminished so as to decrease the sampling frequency of accelerometer. This makes for the system on programmable chip(SOPC) design of digital demodulating system. The upper limit of accelerometer working frequency can reach 3 500 Hz. But affected by the inherent frequency of sensitive components, its working frequency is 10 Hz～1 000 Hz, and the sensitivity is 8.718 0 V/(m·s-2). This accelerometer can detect the dynamic range of acceleration signal real-timely, steadily and accurately, solving the dissymmetrical problem of light path caused by circumstances and the complexity of process.     

Dissymmetrical 3×3 Coupled Optical Accelerometer

Without adding feedback to modulate light path system, the dissymmetrical 3×3 coupled optical accelerometer reduces the complexity of the design of light path system. Experiments prove that it can attain good demodulation effects. As carrier is not needed in this system, the frequency range of input signal is diminished so as to decrease the sampling frequency of accelerometer. This makes for the system on programmable chip(SOPC) design of digital demodulating system. The upper limit of accelerometer working frequency can reach 3 500 Hz. But affected by the inherent frequency of sensitive components, its working frequency is 10 Hz～1 000 Hz, and the sensitivity is 8.718 0 V/(m·s-2). This accelerometer can detect the dynamic range of acceleration signal real-timely, steadily and accurately, solving the dissymmetrical problem of light path caused by circumstances and the complexity of process.     

Bi3+, Eu 3+, Tb3+ 掺杂Lu3TaO7的发光性能研究

采用固相反应法制备了Bi ³⁺ 、Eu³⁺ 、Tb³⁺ 掺杂的Lu₃TaO₇。测量了样品的X射线衍射谱、激发和发射光谱及荧光衰减曲线。三种离子掺杂的Lu₃TaO₇均呈现出强的荧光发射,其中Bi³⁺具有峰位在431 nm处的一强发射宽带,衰减寿命为16.8 μs,Eu ³⁺ 、Tb ³⁺ 则表现出稀土离子的特征锐发射峰,衰减寿命分别为1.26 ms和1.20 ms。因此,它们均是具有潜在应用前景的重闪烁体材料。