La掺杂对(Bi1.5Zn0.5)(Ti1.5Nb0.5)O7陶瓷组织和介电性能的影响

研究了La3+取代的(Bi1.5Zn0.5)(Ti1.5Nb0.5)O7基陶瓷(Bi1.5-xLaxZn0.5)(Ti1.5Nb0.5)O7(0.0≤x≤1 2,BLZNT)的结构与介电性能。采用传统的固相反应法制备了陶瓷样品,用XRD、SEM分析了样品的组织。在整个取代范围内,La3+取代的样品基本保持单一烧绿石相,稳定范围由容忍因子(RA/RB值)来确定;同时,随着La3+取代量的增加,晶胞常数先增后减。介电性能随结构变化而变化,其中介电性能为:ε=130～170,tanδ=～0.9×10-3(1MHz),并且掺杂La优化了BLZNT x样品高频端(>100kHz)的频谱特性。     

Na-Sn掺杂Bi2O3-ZnO-Nb2O5陶瓷的性能

研究了Na+替代Bi3+、Sn4+替代Nb5+对Bi2(Zn1/3Nb2/3)2O7陶瓷烧结特性、显微结构和介电性能的影响.结果表明,替代后样品的烧结温度从1000℃降低到860℃;在-30～130℃样品出现明显的介电弛豫现象;弛豫激活能在0.3eV左右.用缺陷偶极子和晶格畸变对Na-Sn掺杂Bi2(Zn1/3Nb2/3)2O7的介电弛豫现象进行了解释.     

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.     

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.     

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/℃.     

(1-x)(Mg0.7Zn0.3)TiO3-xCa0.61La0.26TiO3系陶瓷的微波介电性能研究（英文）

本实验研究了(1-x)(Mg0.7Zn0.3)TiO3-x(Ca0.61La0.26)TiO3(MZT-CLT)系陶瓷的微观结构和微波介电性能,通过(Ca0.61La0.26)TiO3来协调(Mg0.7Zn0.3)TiO3陶瓷的谐振频率温度系数.MZT-CLT陶瓷的主晶相为(Mg0.7Zn0.3)TiO3,第二相为Ca0.61La0.26TiO3和(Mg0.7Zn0.3)Ti2O5.烧结温度和陶瓷组成对微波介电性能影响显著,当烧结温度为1275℃时,可以获得良好的致密度,当烧结温度超过1300℃时,Zn的蒸发导致陶瓷致密度和介电性能下降.随着(Ca0.61La0.26)TiO3含量的增大,材料的介电常数增大,品质因数减小.当x=0.13,烧结温度为1275℃保温4h,(MZT-CLT)陶瓷具有优良微波介电性能,εr=26,Q.f=86000 GHz,τf=-6×10-6/℃.     

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。     

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。     

Nd3+A位置换对(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3陶瓷微波介电性能的影响

研究了Nd3+离子A位置换改性(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3陶瓷的微波介电性能.[(Pb0.5Ca0.5)1-xNdx](Fe0.5Nb0.5)O3(PCNFN)陶瓷的微波介电性能得到改善是由于少量过剩的Nd3+与(Pb,Ca)2+的固溶能够消除氧空位.当x=0.02时,能够形成单相的钙钛矿相,随着Nd3+置换量的增加,过剩的Nd3+将导致第二相焦绿石的形成,焦绿石会恶化PCNFN的微波介电性能.PCNFN介电性能随x的增加而下降是由于焦绿石相随x增加的结果.当x=0.02-0.05,PCNFN陶瓷有很好的微波介电性能,介电常数K>100,Qf值为5385-5797GHz,频率温度系数TCF随Nd3+含量的增加从正的变为负的.     

半化学法制备（Bi2-xNdx）（Zn1/3Nb2/3）2O7微波介电陶瓷与介电性能的研究

采用半化学法制备微波介电陶瓷（Bi2-xNdx）（Zn1/3Nb2/3）2O7（0≤x≤0.6），系统地研究了陶瓷的相结构及低频介电性能。结果表明：当Nd^3＋取代量较少伍≤0．25）时，样品的相结构仍然保持单斜焦绿石单相，随着Nd^3＋取代量的进一步增加，样品中出现立方焦绿石相，样品结构呈现单斜相与立方相的共存。同时，样品的介电性能随Nd^3＋取代量的变化为：介电常数先增大后减小，而介电损耗先减小后增大，在X=0.25处取得最佳电性能，分另1是εr=83，tanδ=0．0029（100kHz）。     

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.     

Silver cofirable Bi1.5Zn0.92Nb1.5O6.92 microwave ceramics containing CuO-based dopants

Bi₂O₃–ZnO–Nb₂O₅ system has emerged as a good low sintering (1050 °C) microwave material because it exhibits high dielectric constant and low temperature coefficient of resonance frequency (τ_f). We have lowered the sintering temperature of Bi_1.5Zn_0.92Nb_1.5O_6.92 (BZN) below 900 °C by using 3 wt.% of CuO-based dopants, such as 0.21BaCO₃–0.79CuO (BC) and 0.81MoO₃–0.19CuO (MC). The doped BZN exhibits high microwave dielectric constant at 2.3 GHz (k  120). The interfacial behavior between BZN and silver was investigated by using X-ray diffractometer, scanning electronic microscope, and electronic probe microanalyzer. The extent of silver migration of MC and BC dopants is reduced at least by one order of magnitude as compared with V₂O₅ dopant when the samples was prepared at 900 °C for 4 h. Thus, CuO-based dopants can replace V₂O₅ to lower the sintering temperature of BZN and to be cofired with silver.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.     

Thickness-ratio-dependent dielectric properties of Bi1.5Zn1.0Nb1.5O7/Ba0.5Sr0.5TiO3 bilayered thin films

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN)/Ba_0.5Sr_0.5TiO₃ (BST) thin films were prepared on Pt/Ti-coated sapphire substrates by radio frequency magnetron sputtering. The specific relationship between the dielectric properties and the thickness ratio of the BZN thickness to the BST thickness was investigated. The presence of BZN films effectively reduced the dielectric loss of the thin films. The thickness-ratio-dependent dielectric constant and dielectric loss behaviors were in good accordance with the simulation results based on the series connection theory. The optimum thickness ratio was determined to be around 0.5, exhibiting a maximum commutation quality factor of about 16,000. The built-in electric field at the region near the BZN–BST interface may be responsible for the asymmetric characteristic of the electric-field-dependent dielectric properties of the BZN/BST thin films.     

Zinc oxide thin film transistors using MgO-Bi1.5Zn1.0Nb1.5O7 composite gate insulator on glass substrate

We report on high mobility ZnO thin film transistors (TFTs) (< 5 V), utilizing a room temperature grown MgO-Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) composite gate insulator on a glass substrate. 30 mol% MgO added BZN composite gate insulators exhibited greatly enhanced leakage current characteristics (~< 2 × 10^− 8 A/cm² at 0.3 MV/cm) due to the high breakdown strength of MgO, while retaining an appropriate high-k dielectric constant of 32. The ZnO-TFTs with MgO-BZN composite gate insulators showed a high field-effect mobility of 37.2 cm²/Vs, a reasonable on-off ratio of 1.54 × 10⁵, a subthreshold swing of 460 mV/dec, and a low threshold voltage of 1.7 V.     

Large nonlinear optical response of a Bi1.5Zn1.0Nb1.5O7 thin film fabricated by pulsed laser deposition

The Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin film has been fabricated on MgO (001) substrate by pulsed laser deposition. The nonlinear optical properties of the BZN film were investigated using Z-scan technique at a wavelength of 532 nm with 25 ps pulse duration. The two-photon absorption coefficient and the nonlinear refractive index of the BZN film were obtained to be 4.2 × 10^− 6 cm/W and 1.6 × 10^− 10 cm²/W respectively, which are comparable with those of some representative nonlinear optical materials. The large and fast response optical nonlinearities indicated that the BZN film is a promising candidate for future photonics devices.     

Enhanced tunable dielectric properties of Ba0.5Sr0.5TiO3/Bi1.5Zn1.0Nb1.5O7 multilayer thin films by a sol-gel process

Ba_0.5Sr_0.5TiO₃(BST)/Bi_1.5Zn_1.0Nb_1.5O₇(BZN) multilayer thin films were prepared on Pt/Ti/SiO₂/Si substrates by a sol-gel method. The structures and morphologies of BST/BZN multilayer thin films were analyzed by X-ray diffraction (XRD) and field-emission scanning electron microscope. The XRD results showed that the perovskite BST and the cubic pyrochlore BZN phases can be observed in the multilayer thin films annealed at 700 °C and 750 °C. The surface of the multilayer thin films annealed at 750 °C was smooth and crack-free. The BST/BZN multilayer thin films annealed at 750 °C exhibited a medium dielectric constant of around 147, a low loss tangent of 0.0034, and a relative tunability of 12% measured with dc bias field of 580 kV/cm at 10 kHz.     

Influences of post-annealing on structural and electrical properties of Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were prepared on Pt/TiO₂/SiO₂/Si(100) substrates at 650 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The crystallinity, microstructure and electrical properties of BZN thin films were investigated to verify the influences of post-annealing thermal process on them. The X-ray diffractometer (XRD) results indicate that all Bi_1.5Zn_1.0Nb_1.5O₇ thin films without post-annealing process or with post-annealing in situ vacuum chamber and in oxygen ambient exhibit a cubic pyrochlore structure. The improved crystallinity of BZN thin films through post-annealing was confirmed by XRD and scanning electron microscope (SEM) analysis. Dielectric constant and loss tangent of the as-deposited BZN thin films are 160 and 0.002 at 10 kHz, respectively. After annealing, dielectric properties of thin films are significantly improved. Dielectric constant and loss tangent of the in situ annealed films are 181 and 0.0005 at 10 kHz, respectively. But the films post-annealed in O₂ oven show the largest dielectric constant of 202 and the lowest loss tangent of 0.0002, which may attribute to the increase in grain size and the elimination of oxygen vacancies. Compared with the as-deposited BZN thin films, the post-annealed films also show the larger dielectric tunability and the lower leakage current density.     

Structure and microwave dielectric properties of Bi1.5Zn1.0Nb1.5O7 thin films deposited on alumina substrates by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were deposited on polycrystalline alumina substrates by pulsed laser deposition at different substrate temperatures. The phase structure and surface morphology were characterized using X-ray diffractometer (XRD) and atomic force microscopy. Microwave dielectric properties were performed using split-post dielectric resonator method at spot frequencies of 10, 15 and 19 GHz, respectively. The XRD results indicate that the as-deposited Bi_1.5Zn_1.0Nb_1.5O₇ thin films deposited at 650 °C are amorphous in nature. The dielectric permittivity and loss tangent of the amorphous BZN thin films are 75.5 and 0.013 at 10 GHz, respectively. As the measure frequency increased to 19 GHz, the dielectric permittivity slightly decreases and loss tangent slightly increases. BZN thin films were crystallized after the post-annealing by a rapid thermal annealing in air for 30 min. The crystallized BZN thin films exhibit the excellent dielectric properties and frequency responses. The dielectric permittivity and loss tangent of the crystallized BZN thin films are 154 and 0.038 at 10 GHz, respectively.