La2O3掺杂对BST/MgO复合陶瓷显微结构和性能的影响

采用固相反应法制备了未掺杂和La2O3掺杂(0.5%、1%、2%(摩尔分数))的Ba0.55Sr0.45TiO3/MgO复合陶瓷材料,并研究了它们的显微结构和各种介电性能.研究结果表明,La2O3除一部分会进入BST晶格獭代Ba或Sr的位置外,还会有一部分与MgO等形成无定形态物质滞留在晶界,起到抑制BST晶粒生长的作用.BST/MgO复合陶瓷的居里温度随La2O3掺杂量的增大而降低,居里温度的降低导致了介电常数的减小.适量的La2O3掺杂提高了复合陶瓷的调谐性,而且La2O3掺杂明显降低了复合陶瓷的微波介电损耗.0.5%(摩尔分数)La2O3掺杂的BST/MgO复合陶瓷具有最佳的综合介电性能,其在10kHz下的调谐性为6.9%(2kV/mm),3.99GHz时的介电常数和介电损耗分别为87.5和3.35×10-3,基本可以满足铁电移相器的使用要求.     

Effect of ZrO2 doping on the tunable and dielectric properties of Ba0.55Sr0.45TiO3/MgO composites for microwave tunable application

Undoped and ZrO₂ doped (0.5, 1.0, 2.0, 3.0 wt.%) Ba_0.55Sr_0.45TiO₃/MgO composites were prepared by traditional ceramic processing. The ZrO₂ doping effect on the structural, surface morphological, tunability and dielectric properties were systemically investigated. The result shows that the tunability of Ba_0.55Sr_0.45TiO₃/MgO composites was improved by using ZrO₂ dopant. The Ba_0.55Sr_0.45TiO₃/MgO composite with 1.0 wt.% ZrO₂ dopant exhibits high tunability (17% at 2.5 kV/mm), low dielectric constant (200) and a low microwave loss (0.005, 2.7 GHz), which are suitable for microwave tunable application.     

Effect of MnCO3 doping on the dielectric and tunable properties of BSTO/MgO composite for phased array antennas

Undoped and MnCO₃ doped (0.3, 0.5, 1, 2mol%) Ba_0.55Sr_0.45TiO₃/MgO composites were prepared by conventional ceramic processing method and their structural, surface morphological, tunable properties and their dielectric properties at low and microwave frequencies were extensively investigated. The results indicate that the addition of MnCO₃ slightly decreases the average grain size. The proper doping of MnCO₃ can dramatically improve the properties of Ba_0.55Sr_0.45TiO₃/MgO composite with lower dielectric loss and higher tunability. For 0.5mol% MnCO₃ doped samples, the microwave loss at 4.19 GHz is 2.91 × 10⁻³ and the value of tunability is 7.4% with the external DC field 2 kV mm⁻¹, which presented the best properties and can basically meet the requirements of phased array applications.     

Microstructure and dielectric properties of BST/MZO ceramic composites for tunable microwave applications

Ba_0.6Sr_0.4TiO₃/Mg_0.9Zn_0.1O (BST/MZO) ceramic composites with different MZO contents were prepared by traditional ceramic process. The crystal structure, fracture surface morphology, and dielectric properties were systematically investigated. The results show that the BST/MZO ceramic composites possess diphase structure, dense, and uniform morphology. The composites have relatively low dielectric loss (in the order of 10⁻³) at microwave frequency. The ceramics all retain substantial tunability (more than 20% at 8 kV/mm DC field) and excellent dielectric strength (more than 19.5 kV/mm). The BST-50 wt% MZO sample has the optimal FOM value (about 256) and should be a better candidate for tunable microwave applications.     

MgO/La2O3CO3复合材料对磷酸盐的吸附特征

采用水热法制备了MgO/La2 O2 CO3复合材料(ML).采用X射线衍射仪和扫描电子显微镜对其结构及表面形貌进行了表征,利用Zeta电位仪测定了其零点电位点,并探究了接触时间、初始磷酸盐浓度和初始pH对磷酸盐吸附效果的影响.结果 表明,ML呈现板块状堆叠而成的层状结构,零点电位点为4.52.准二级动力学模型和Fre...     

La2O3掺杂对ZnNb2O6陶瓷微观缺陷和介电常数的影响

通过测量不同La2O3含量的ZnLa2xNb2(1-x)O(6-2x)微波介质陶瓷的介电常数、符合正电子湮没辐射多普勒展宽谱和寿命谱,研究不同La2O3含量对该陶瓷介电常数和微观缺陷的影响。结果表明,x0.20时,随着La2O3含量增加,样品正电子平均寿命τm和缺陷浓度减小,致密度、商谱谱峰和介电常数εr升高。x=0.20时,样品正电子平均寿命τm和缺陷浓度最小,致密度、商谱谱峰和介电常数εr最高。x≥0.30时,样品正电子平均寿命τm和缺陷浓度升高,致密度、商谱谱峰和介电常数εr降低。     

Effect of nickel on microwave dielectric properties of Ba(Mg1/3Ta2/3)O3

The dielectric and physical properties of the complex perovskite Ba(Mg_1/3Ta_2/3)O₃ system in which magnesium was substituted for nickel from 0.03–0.67 mol%, were investigated in the temperature range 20–110C, and the frequency range 10.5–14.5 GHz. As the nickel content was increased, the dielectric constant, the degree of ordering, and the unloaded Q decreased. The temperature dependence of the dielectric constant and the temperature coefficient of resonant frequency of the specimens annealed at 1500C for 20 h were found to be greater than those of the specimens sintered at 1650C for 2 h. These results are due to the increase in the density, the increase in grain size, and the lattice distortion.     

Al掺杂对SiC粉体微波介电性能的影响

采用高温固相反应法,以Al粉和SiC粉为原料合成Al掺杂SiC粉体。通过X射线衍射分析和拉曼光谱对合成粉体进行了表征。结果表明,当反应温度高于1900℃时,合成产物中未出现Al的杂质相。在2000℃时,相对较多的Al原子进入到SiC晶格形成Al-SiC固溶体。在8.2～12.4GHz频率范围,采用波导法对未掺杂和掺杂SiC粉体的介电常数进行了测试。结果表明,Al原子掺杂形成Al-SiC固溶体,可以有效地提高SiC粉体的微波介电性能。     

Effect of B2O3 addition on the microstructure and microwave dielectric properties of Li2CoTi3O8 ceramics

The effects of B₂O₃ addition on the sintering behavior, microstructure and microwave dielectric properties of the Li₂CoTi₃O₈ ceramics were investigated. The variations of microstructure and composition of Li₂CoTi₃O₈ ceramics were observed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. The small amount of B₂O₃ addition could not only effectively lower the sintering temperatures, but also reduce the temperature coefficient of resonant frequency (τ _f ) of Li₂CoTi₃O₈ ceramics. The Li₂CoTi₃O₈ ceramic with 2.0 wt% B₂O₃ addition sintered at 900 °C exhibits good microwave dielectric properties with a ε _r of 26.6, a Q × f value of 21,300 GHz and a small τ _f of 1.78 ppm/°C. Moreover, B₂O₃-added Li₂CoTi₃O₈ ceramic has a chemical compatibility with silver, which makes it a promising ceramic for LTCC technology application.     

等离子喷涂ZnO/Al2O3涂层微波介电特性研究

采用等离子喷涂工艺,以氧化锌(ZnO)作为吸收剂,氧化铝(Al2O3)为填料,聚乙烯醇(PVA)为粘结剂制备成ZnO/Al2O3复合涂层。分析了复合涂层的相组成及微观结构,研究了氧化锌含量对复合涂层介电性能的影响。结果表明,经喷涂后的涂层中有新相ZnAl2O4生成,其含量随原料中ZnO的含量增加而增加。涂层的密度与涂层中氧化锌含量有关。介电性能测试表明,涂层中ZnO含量的增加使涂层介电常数实部(ε′)及损耗(tanδ)先增加后降低。ZnO摩尔含量为65%时,随频率的增加,涂层介电常数呈降低的趋势。     

Effect of La2O3 doping on the microstructure and electrical properties of a SnO2-based varistor

The effect of La₂O₃ addition on the densification and electrical properties of the (0.9895-xSnO₂+0.01CoO+0.0005Nb₂O₅+x La₂O₅ system, where x=0.0005 or 0.00075, was considered in this study. The samples were sintered at 1300 °C for 2 and 4 h and a single SnO₂ phase was identified by X-ray diffraction. Microstructure analysis by scanning electron microscopy showed that the affect of La₂O₃ addition is to decrease the SnO₂ grain size. J versus E curves indicated that the system exhibits a varistor behavior and the effect of La₂O₃ is to increase both the non-linear coefficient () and the breakdown voltage (E₂). Considering the Schottky thermionic emission model the potential height and the width were estimated. The addition of small amounts of La₂O₃ to the basic system increases the potential barrier height and decreases both grain size and potential barrier width. © 2001 Kluwer Academic Publishers     

ZnAl_2O_4和La_2O_3对Ca_(0.61)Nd_(0.26)TiO_3-MgTiO_3复合陶瓷介电性能的影响

通过传统的固相反应合成掺杂ZnAl_2O_4和La~(3+)(来自La_2O_3)的Ca_(0.61)Nd_(0.26)TiO_3-MgTiO_3复合陶瓷粉体,干压成型后在空气气氛下常压烧结制备ZnAl_2O_4和La~(3+)掺杂Ca_(0.61)Nd_(0.26)TiO_3-MgTiO_3复合陶瓷样品。分别研究了La~(3+)和ZnAl_2O_4的掺杂量对复合陶瓷样品的微观形貌、相组成和介电性能的影响。结果表明:ZnAl_2O_4具有细化晶粒的作用;Ca_(0.61)Nd_(0.26)TiO_3-MgTiO_3复合陶瓷样品的致密度随La~(3+)和ZnAl_2O_4含量的增加而增加;介电常数和谐振频率温度系数随ZnAl_2O_4含量的增加而减小,随La_2O_3添加量变化不大;品质因数值随ZnAl_2O_4含量的增加先增加后减小。制备出的ZnAl_2O_4和La~(3+)掺杂Ca_(0.61)Nd_(0.26)TiO_3-MgTiO_3复合陶瓷致密度达到94%以上,介电常数在40~50之间,谐振频率温度系数小于40×10~(-6)℃~(-1),品质因数大于38 000GHz,可以用于通信技术领域。     

Effect of B2O3 additive on the sintering temperature and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 ceramics

Journal of Materials Science: Materials in Electronics - This paper reported a research of the sinterability, microstructures, and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 (BMT) ceramics...     

PbO-B2O3基玻璃对(Pb,Ca,La)(Fe,Nb)O3陶瓷微波介电性能的影响

基于玻璃形成理论和能量最小原理了玻璃组元与PCLFN陶瓷的微波介电性能之间的关系。PbO-B2O3基玻璃添加剂能够降低PCLFN陶瓷的烧结温度100－150℃。当PCLFN在1000－1050℃空气中烧结，Qf=3945-4796GHz，介电常数K＝100。PbO-B2O3基玻璃的组成也会影响PCLFN陶瓷的微波介电性能。三种PbO－B2O3基玻璃中，PbO-B2O3-V2O5玻璃是最有效的烧结助剂。     

Effect of B2O3 and CuO additives on the sintering temperature and microwave dielectric properties of Ba(Mg1/3Nb2/3)O3 ceramics

B₂O₃ added Ba(Mg_1/3Nb_2/3)O₃ (BBMN) ceramics cannot be sintered below 930 °C. However, when CuO was added to them, they were sintered even at 850 °C. The amount of the Ba₂B₂O₅ second phase, which was formed in the BBMN ceramics decreased with the addition of CuO. Therefore, the CuO additive is considered to react with the B₂O₃ inhibiting the reaction between B₂O₃ and BaO. A dense microstructure without pores developed with the addition of a small amount of CuO. The bulk density, dielectric constant (ɛ_r) and Q-value increased with the addition of CuO, but decreased when a large amount of CuO was added. Excellent microwave dielectric properties were obtained for the Ba(Mg_1/3Nb_2/3)O₃ + 2.0 mol% B₂O₃ + 10.0 mol% CuO ceramic sintered at 875 °C for 2 h, with values Q_xf = 21 500 GHz, ɛ_r = 31 and temperature coefficient of resonance frequency (τ_f) = 21.3 ppm/°C.