脉冲激光沉积法制备立方焦绿石结构的Bi1.5ZnNb1.5O7薄膜

采用固相反应法合成具有焦绿石立方结构的Bi1.5ZnNb1.5O7(BZN)陶瓷靶材,采用脉冲激光沉积法在Pt/SiO2/Si(100)基片制备立方BZN薄膜。研究了随衬底温度的变化,薄膜的结晶性能,微观形貌以及介电性能的差异。结果表明当衬底温度在550~650℃时,薄膜具有纯的立方BZN结构,并且在600℃时薄膜的晶粒发育比较完整,此时薄膜具有较高的介电常数和较低的损耗。     

影响Bi1.5ZnNb1.5O7纳米粉体水热合成因素的研究

以分析纯的Bi（N03）3·5H2O，ZnO和Nb2O5为反应物，KOH为矿化剂，采用水热法合成立方焦绿石结构的Bi1.5ZnNb1.5O7纳米粉体，通过XRD对合成粉体进行物相分析，并通过Scherrer公式计算粉体晶粒的尺寸；TEM分析所合成粉体的形貌。研究水热反应温度、时间、前躯体的含量、KOH的浓度以及有无搅拌等水热合成条件的变化对合成粉体的物相的影响，从而初步确定水热合成立方焦绿石结构的Bi1.5ZnNb1.5O7纳米粉体的温度区间、时间范围、前驱体含量和KOH浓度等工艺参数，并讨论了其反应过程。研究结果表明，在Nb：Bi=2.0、KOH浓度为1.8mol／L、反应温度为220℃、反应时间为24h、充分搅拌的情况下，水热反应进行得最彻底，可以合成单相的Bi1.5ZnNb1.5O7纳米粉体。     

Sm2O3掺杂Bi2O3-ZnO-Nb2O5基陶瓷的结构与性能

研究了Sm2O3掺杂的bi2O3-ZnO-Nb2O5(BZN)基陶瓷(Bi1.5-xSmxZn0.5)(Zn0.5Nb1.5)O7(O≤x≤0.6,BSZN),的结构及介电性能.结果表明纯BZN陶瓷的结构为立方焦绿石单相;当Sm2O3掺杂量较少(O＜x≤0.5)时,样品的相结构仍然保持立方焦绿石单相;随着Sm2O3掺杂量的进一步增加(x≥0.6),样品出现其它相.同时,试样的介电性能随结构的变化而呈现有规律的变化.     

Y3+取代Bi3+的Bi2O3-ZnO-Nb2O5基陶瓷的结构与介电性

研究了Y3 取代的Bi2O3-ZnO-Nb2O5(BZN)基陶瓷(Bi1.5-xYxZn0.5)(Zn0.5Nb1.5)O7(0≤x≤1.5,BYZN)的结构和介电性能.采用传统的固相反应法制备陶瓷样品,XRD分析样品的相结构,SEM分析样品的微观形貌.结果表明:BZN陶瓷的结构为立方焦绿石单相;当Y3 取代量较少(0＜x≤0.3)时,样品的相结构仍然保持立方焦绿石单相;随着Y3 取代量的进一步增加(x≥0.6),样品由立方焦绿石相向YNbO4和ZnO复相过渡.同时,样品的介电性能随结构的变化而呈现有规律的变化.     

Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7陶瓷结构与介电性能的影响

研究了Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷烧结特性、相结构和介电性能的影响.采用传统的固相反应法制备样品,X射线衍射技术分析相结构,SEM观察表面形貌.结果表明,Bi4Ti3O12掺杂能有效地促进烧结,提高介电常数ε,降低介电损耗tgδ,优化介电频率温度系数αε.1000℃烧结8%(摩尔分数) Bi4Ti3O12掺杂的BZN陶瓷具有较好的介电性能ε=192,tgδ= 4.21×10-4,αε=-3.37×10-4/℃.     

脉冲激光沉积ZrW2O8薄膜的制备和性能

采用脉冲激光沉积法在石英基片上沉积制备了ZrW2O8薄膜.用X射线衍射仪(XRD)、原子力显微镜(AFM)研究了不同衬底温度对薄膜结构组分、表面粗糙度和形貌的影响,用台阶仪和分光光度计测量薄膜的厚度和不同衬底温度下制备薄膜的透射曲线,用变温XRD分析了ZrW2O8薄膜的负热膨胀特性.实验结果表明:在衬底温度为室温、550℃和650℃下脉冲激光沉积的ZrW2O8薄膜均为非晶态,非晶膜在1200℃保温3min后淬火得到立方相ZrW2O8薄膜;随着衬底温度的升高,ZrW2O8薄膜的表面粗糙度明显降低;透光率均约为80%,在20～600℃温度区间内,脉冲激光沉积制备的ZrW2O8薄膜的负热膨胀系数为-11.378×10-6 K-1.     

Bi基焦绿石结构陶瓷的介电频率特性

在低频、射频和微波波段频率下,借助HP4192A阻抗分析仪和HP8720ET/ES网络分析仪,对3种Bi基焦绿石结构介电陶瓷材料BZN[(Bi1.5Zn0.5)(Zn05Nb1.5)O7]、BZS[(Bi1.5Zn05)(Zn0.5Sb1.5)O7]和BCZN[(Bi1.5Ca0.5)(Zn0.5Nb1.5)O7]的介电频率特性进行了分析研究.结果发现:介电常数随着Bi基焦绿石结构中氧八面体间隙增大而增大;从低频到射频,BZN(ε≈160)、BZS(ε≈42)和BCZN(ε≈81)三体系介电常数都较高且很稳定,其介质损耗都很低(Tanδ≈10-4);在微波频段(4GHz)下,介电常数分别约为98.596、30.573和56.451.     

Bi1.5-xCaxZnNb1.5O7陶瓷结构、介电性能与结晶化学特性

采用固相反应法制备Bi1.5-xCaxZnNb1.5O7(0≤x≤0.50,BCZN)陶瓷,研究Ca2+替代Bi3+对Bi1.5ZnNb1.5O7陶瓷烧结特性、显微结构、介电性能和结晶化学特性的影响.结果表明:替代量x≤0.25 mol时,样品为单一的α-BZN相.随着Ca2+替代量增加,样品最佳烧结温度从1000℃升高到1020℃;致密度从7.011 g/cm3减小到6.353 g/cm3;样品晶粒尺寸、晶格常数、电阻率均减小;结晶化学参数键价和,AV(O’)[Bi4]、AV(O’)[Bi3Zn]、AV(O’)[Bi2Zn2]和AV(O’)[Ca3Zn]均增大,且该行为与其晶格常数、介电性能变化相吻合.     

Bi2O3—ZnO—Nb2O5系中焦绿石结构与相分布

根据焦绿石结晶化学原理，研究了Bi2O3－ZnO－Nb2O5（BZN）系中焦绿石的相结构与分布用淬冷技术保持样品的高温相结构，用粉末X-射线衍射技术（XRD）分析相组成与相结构得到了BZN系中两种焦绿名单相（立方相α和正交相β和α-β复相分布的等温相图，并探讨了该系统中焦绿石立方相和正交相之间的α-β位移式相变的机理     

退火温度对ZnO陶瓷薄膜低压压敏特性的影响

应用新型溶胶-凝胶法制备了ZnO陶瓷薄膜,研究了退火温度对ZnO陶瓷薄膜低压压敏电阻电性能的影响.结果表明,采用溶胶掺杂在550℃退火条件下可形成Zn7Sb2O12及ZnCr2O4相,且在退火温度范围内(550～950℃)基本上没有焦绿石相形成.当退火温度达到750℃以后,Sb2O3已全部转变为稳定性好的尖晶石相,同时存在Bi2O3、ZnO的挥发.采用适当的退火温度,可得到具有优良电性能的ZnO陶瓷薄膜低压压敏电阻,其压敏电压低于5 V,非线性系数可达20,漏电流密度小于0.5μA/mm2.     

High-Purity As2S1.5Se1.5 Glass Optical Fibers

Core–clad optical fibers were fabricated from high-purity As₂S_1.5Se_1.5 glass, and their properties were studied. The arsenic sulfo-selenide was prepared by melting a mixture of high-purity arsenic monosulfide, arsenic, and selenium. Optical fibers with core/clad diameters of 300/400 and 200/400 m were fabricated by the double-crucible method. The minimum loss was found to be 60 ± 20 dB/km at 4.8 m and 200–300 dB/km between 4 and 6 m. The numerical aperture of the fibers was 0.28. A 1.5-m-long section of the fiber transmitted 6-W CO laser radiation. The average bending strength of the 400-m-diameter fibers was 0.8 GPa.     

Cadmium substituted (Bi1.5ZnNb1.5)O7 dielectric ceramics

The effects of small amounts of Cd substitution for Zn in the low loss dielectric material Bi_1.5ZnNb_1.5O₇ are reported. Solid solution of (Bi_1.5Zn_0.5-x Cd _x )(Zn_0.5Nb_1.5)O₇ was formed in the present ceramics for x < 0.1, and β-Bi₂O₃ secondary phase appeared at x = 0.3. For x = 0.5, another phase Bi_1.6Cd_0.4O_2.8 appeared gradually with increasing x. With increasing x, the dielectric constant increased firstly and reached their maximums 168 at 1 MHz, then decreased after x > 0.2. High-ɛ dielectric ceramics with low dielectric loss were created at the composition x = 0.2: ɛ = 168, and α_ɛ = − 554 ppm/° at 1 MHz.     

Materials with mixed conductivity in a HfO2-YO1.5-PrO1.5 system

The phase composition and electrical properties of HfO₂-YO_1.5-PrO_1.5 systems have been determined. Studies have been made to identify how the specific electrical properties of these solid solutions are influenced by praseodymium oxide additives when the yttrium oxide content is constant, and how they are influenced by the interchangeability of praseodymium oxide with yttrium oxide when the hafnium dioxide content is kept constant. Pis’ma Zh. Tekh. Fiz. 23, 14–17 (April 12, 1997)     

Structure and dielectric properties of Nd substituted Bi1.5MgNb1.5O7 ceramics

New pyrochlore ceramics Bi_(1.5?x)Nd _x MgNb_1.5O₇ with x = 0–0.6 were synthesized by doping Nd into the A site in the Bi_1.5MgNb_1.5O₇ pyrochlore. The Nd substituted Bi_1.5MgNb_1.5O₇ ceramics were prepared utilizing solid-state reaction and investigated by X-ray diffraction, scanning electron microscope and dielectric measurements. The crystal structure was characterized as single cubic pyrochlore phase for x ≤ 0.5 while the second phase appeared at x = 0.6. With increasing Nd content from 0 to 0.5, the lattice parameters decreased slightly and the average grain size pronouncedly reduced from ~7.5 to ~5.0 μm. The Nd incorporation resulted in attractive enhancement of the dielectric properties including the temperature coefficient of dielectric constant that was remarkably optimized with the lowest value of ?16 ppm/°C at x = 0.5. A good combination of low dielectric loss, superior temperature coefficient and high dielectric permittivity can be achieved for the composition of x = 0.5, which seems to be very appealing for the practical use in high-frequency multilayer ceramic capacitors.     

Microstructure,mechanical property and wear behavior of AlCrFe1.5Ni1.5 medium entropy alloy

Journal of Materials Science - In present study, a cost-effective Co-free AlCrFe1.5Ni1.5 medium entropy alloys (MEAs) have been developed by vacuum melting technology. The microstructure of the...     

CeO1.5-stabilized tetragonal ZrO2

Ceria-stabilized tetragonal zirconia polycrystals show high toughness and high resistance to the low-temperature ageing degradation. However, ceria is less effective in stabilizing tetragonal zirconia compared to yttria and other trivalent oxides. The tetravalent oxide of CeO₂ can be easily reduced to the trivalent CeO_1.5, but phase separations occur leading to the destabilization of the tetragonal phase or the stabilization of the cubic phase. A procedure of high-temperature sintering and low-temperature reduction has been developed for preparing CeO_1.5-stabilized tetragonal zirconia. It was found that 9 mol% CeO_1.5 could stabilize the tetragonal zirconia to room temperature and that the stability region in the CeO_1.5-ZrO₂ system was extended to the lower dopant content region. The CeO_1.5-stabilized tetragonal zirconia had a lower tetragonality and lower transformability compared to the CeO₂-stabilized tetragonal zirconia with the same dopant mole percentage. The changes in the phase composition, tetragonality and stability caused by the reduction of CeO₂ to CeO_1.5 have been discussed in relation to the changes of oxygen stoichiometry, which is considered of the firstorder importance in the stabilization of polymorphous zirconia.     

激光熔覆Co1.5CrFeNi1.5Ti0.75Nbx高熵合金的组织和性能研究

目的 研究Nb含量对高熵合金Co1.5CrFeNi1.5Ti0.75Nbx熔覆层组织和性能的影响.方法 在H13钢表面制备了Co1.5CrFeNi1.5Ti0.75Nbx(x=0.25,0.50,0.75,1.00,原子数分数)高熵合金熔覆层,研究Nb含量对熔覆层的物相组织、微观结构、硬度和耐磨性的影响.结果 高熵合金熔覆层主要为BCC相、FCC相和Laves相的组织.在熔覆层中添加Nb,Laves相随之增加,组织的微观形貌发生变化.熔覆层的硬度远远高于H13钢(退火态),Co1.5CrFeNi1.5Ti0.75Nb0.5熔覆层的平均硬度最高,约为H13钢(退火态)的2.8倍.Co1.5CrFeNi1.5Ti0.75Nb0.5熔覆层的摩擦磨损失重最小,磨损程度更低,耐磨性更好.结论 Nb元素加入高熵合金体系会形成Laves相,Laves相能够提高高熵合金的力学性能.相关结果 对于高熵合金体系的研究具有一定意义,为高熵合金的成分设计和优化提供了必要的实验支持.     

A novel green emitting phosphor Ca1.5Y1.5Al3.5Si1.5O12:Tb

Vacuum ultraviolet (VUV) excitation and emission properties of Tb³⁺ ion doped silico-aluminate phosphor Ca_1.5Y_1.5Al_3.5Si_1.5O₁₂:Tb³⁺ was studied. Upon excitation with vacuum ultraviolet (VUV) and near UV light excitation, the phosphor showed strong green-emission peaked at 545 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺, and the highest PL intensity at 545 nm was found at a content of about 14 mol% Tb³⁺. The 4f–5d transition absorption of Tb³⁺ is in the range from 150 nm to 260 nm, and there is an energy transfer from the host to the rare earth ions. Field emission scanning electron microscopy (FE-SEM) images showed the particle size of the phosphor was less than 3 μm.