Ba1-3x/2Lax(Mg1/3Ta2/3)O3陶瓷的微波介电性能

采用固相合成法制备了Ba1-3x/2Lax(Mg1/3Ta2/3陶瓷,研究了La掺杂对钽镁酸钡的结构和微波介电性能的影响.结果表明:A位取代能改进其烧结性能.在x≤0.02时,烧结样品为单相的钙钛矿结构,B位离子1:2有序;当x>0.02时出现第二相Ba0.5TaO3.B位离子有序度随着x的增大先增加后减小,在x=0.04时出现最大值.x≤0.02时介电常数变化较小,而后其值逐渐增大.品质因数与谐振频率的乘积(Q×f)值随着x的增大先增大后减小,在x=0.02时取得最大值;谐振频率温度系数(τf)值随着x增大而增大.     

Ba（1-3x/2）Lax（Mg（1/3）Ta（2/3））O3陶瓷的微波介电性能（英文）

采用固相合成法制备了Ba1–3x/2Lax（Mg1/3Ta2/3）O3陶瓷,研究了La掺杂对钽镁酸钡的结构和微波介电性能的影响。结果表明：A位取代能改进其烧结性能。在x≤0.02时,烧结样品为单相的钙钛矿结构,B位离子1：2有序;当x〉0.02时出现第二相Ba0.5TaO3。B位离子有序度随着x的增大先增加后减小,在x=0.04时出现最大值。x≤0.02时介电常数变化较小,而后其值逐渐增大。品质因数与谐振频率的乘积（Q×f）值随着x的增大先增大后减小,在x=0.02时取得最大值;谐振频率温度系数（τf）值随着x增大而增大。     

SrCO3掺杂对BMT陶瓷结构及介电性能的影响

采用固相烧结法制备SrCO3掺杂Ba（Mg1/3Ta2/3）O3（BMT）微波介质陶瓷,研究SrCO3质量（下同）掺量w（SrCO3）=2%～8%对BMT微波介质陶瓷结构和介电性能的影响。结果表明：添加适量SrCO3可以促进烧结并在一定程度上提高BMT陶瓷体系的B位离子1：2有序度;当w（SrCO3）=6%时,陶瓷致密...     

铋层状化合物Sr0.3Ba0.7Bi4-xLaxTi4O15陶瓷材料的介电性能

采用固相烧结工艺制备了铋层状化合物Sr0．3Ba0.7Bi4-xLaxTi4O15铁电陶瓷。X射线衍射证实：La含量很大的范围内(x=0～1)均形成了层状钙钛矿结构固熔体。Sr0.3Ba0.7Bi3.25La0.75Ti4O15粉料在低温下难以烧结,随着烧结温度的提高,Sr0．3Ba0.7Bi4-xLaxTi4O15陶瓷密度增加的同时,产生焦绿石相,但La的加入在一定程度上抑制焦绿石相的形成．Sr0．3Ba0.7Bi4-xLaxTi4O15陶瓷的介电常数峰在10kHz时较宽,在100Hz时,介电常数峰被随温度升高而逐渐增大的介电常数所“屏蔽”,材料损耗角正切随温度升高而增大,在低频下增加得更快。     

Bi_2O_3/Li_2O助熔剂BST介电陶瓷的低温烧结研究

采用固相反应制备了低温烧结(Ba0.71Sr0.29)TiO3-x Bi2O3/Li2O(x=0.02、x=0.03、x=0.05)陶瓷,差热分析结果表明助熔剂Bi2O3/Li2O可降低(Ba0.71Sr0.29)TiO3陶瓷的烧结温度至820℃并获得相对密度为97%的BST陶瓷。X射线衍射发现制备过程有少量次生相生成,分别为Li2TiO3和Ba2TiO4。实验结果表明Bi2O3/Li2O助熔剂降低了(Ba0.71Sr0.29)TiO3的铁电性,这也是导致介电常数和介电损耗降低的原因。低温烧结机理涉及碳酸钡的中间体的形成,Li离子的熔融态迁移至BST结构中提供了促进反应进行的液相。     

弛豫铁电陶瓷Ba(Mg,Nb)O_3的制备及性能研究

采用传统陶瓷烧结方法,在空气气氛下烧结制得Ba(Mg,Nb)O3(BMN)陶瓷,并分析了烧结温度对体系相组成及相结构的影响。X射线衍射(XRD)研究表明,随着烧结时间的增加,体系中钙钛矿相也相应增加。红外(FTIR)研究研究表明结构无序的BMN钙钛矿相中部分的区域出现了结构有序现象。通过X射线光电子能谱(XPS)可以发现,随着烧结温度的增加,体系中Nb2O5进入Ba(Mg1/3,Nb2/3)O3晶格。微波介电性能表明,随着烧结温度的增加,Ba(Mg,Nb)O3的rε和Qf值有逐渐增加的趋势。     

添加剂对Ba(Zn1/3Nb2/3)O3-Sr(Zn1/3Nb2/3)O3陶瓷介电性能的影响

研究了MnCO3,BaZrO3对0.35Ba(Zn1/3Nb2/3)O3(BZN)-0.65Sr(Zn1/3Nb2/3)O3(SZN)陶瓷介电性能的影响.研究表明:添加MnCO3,BaZrO3时,对陶瓷的烧结均起促进作用,增大介电常数.加入1%(质量分数)的MnCO3可使陶瓷具有较小的介质损耗,同时MnCO3对陶瓷的介电常数温度系数具有正向调整作用.加入BaZrO3后通过生成液相而减少了第二相Ba5Nb4O15,BaNb2O6的生成.所制备的(0.35BZN0.65SZN)+0.1%MnCO3陶瓷的εr≈43.6,αe≈-8×10-6/K,tanδ＝0.6×10-4,且烧结温度低于1 300℃.     

添加剂对Ba(Zn_(1/3)Nb_(2/3))O_3-Sr(Zn_(1/3)Nb_(2/3))O_3陶瓷介电性能的影响

研究了MnCO3,BaZrO3对 0 .35Ba(Zn1 /3Nb2 /3)O3(BZN) -0 .65Sr(Zn1 /3Nb2 /3)O3(SZN)陶瓷介电性能的影响。研究表明 :添加MnCO3,BaZrO3时 ,对陶瓷的烧结均起促进作用 ,增大介电常数。加入 1% (质量分数 )的MnCO3可使陶瓷具有较小的介质损耗 ,同时MnCO3对陶瓷的介电常数温度系数具有正向调整作用。加入BaZrO3后通过生成液相而减少了第二相Ba5Nb4O1 5,BaNb2 O6 的生成。所制备的 ( 0 .35BZN -0 .65SZN) 0 .1%MnCO3陶瓷的εr≈ 43.6,αε≈ -8× 10 - 6 /K ,tanδ =0 .6× 10 - 4 ,且烧结温度低于 130 0℃。     

Bi4B2O9对(Ca0.2Sr0.05Li0.375Sm0.375</sub>TiO3陶瓷烧结和微波介电性能的影响

采用传统固相法制备(Ca0.2Sr0.05Li0.375Sm0.375)TiO3钙钛矿微波介质陶瓷,研究了Bi4B2O9对(Ca0.2Sr0.05Li0.375Sm0.375)TiO3陶瓷微波介电性能的影响,利用X射线衍射仪、扫瞄电子显微镜和矢量网络分析仪对其晶体结构、显微组织和微波介电性能进行了研究。结果表明:掺10%Bi4B2O9的(Ca0.2Sr0.05Li0.375Sm0.375)TiO3陶瓷,其烧结温度由1 300℃降至1 080℃。当添加3.5%Bi4B2O9时,其最佳烧结温度为1 150℃,陶瓷的微波介电性能最佳(相对介电常数εr=116.9;品质因数Q×f=3 500GHz;频率温度系数τf=1.2×10-6/℃)。     

B2O3-Li2O掺杂低温烧结Ba0.6Sr0.4TiO3陶瓷的介电性能

采用传统陶瓷制备工艺,通过B2O3-Li2O的有效掺杂,低温液相烧结制备了Ba0.6Sr0.4TiO3(BST)陶瓷,并对其介电性能进行了研究.X射线衍射分析和介电性能测试结果表明:适量B2O3-Li2O掺杂的BST陶瓷,经97S℃烧结4h,所得样品的主晶相为钙钛矿结构,未出现明显的杂相;随B2O3-Li2O掺杂量的增加,BST陶瓷材料的介电常数减小,Curie峰变得弥散宽化,介电损耗则与未掺杂BST陶瓷的保持一致,即在0.003以下:适量B2O3-Li2O的掺杂对BST陶瓷材料的Curie温度和介电调制性能影响不大.     

ICP-AES原子发射分析法检测LiNi1/3Co1/3Mn1/3O2中Ni含量

建立了一套可用于实际电池及材料生产、研制的电池材料镍钴锰酸锂中Ni的测定方法。在解决了原子发射法的基体效应及光谱干扰问题后,选定合适的分析条件,进行方法的准确度和精密度实验,数据结果显示方法可以满足实际分析工作的要求。     

Ferroelectric Ceramics in the PbMg1/3Nb2/3O3-PbCd1/3Nb2/3O3 System

Solid solutions (1-x)PbMg_1/3Nb_2/3O₃ + xPbCd_1/3Nb_2/3O₃ with x = 0-0.30 are investigated with purpose to work out a capacitor ceramics with good dielectric properties and low sintering temperature. It is found that the perovskite phase forms at sintering near to 980°C and begins to decompose at higher temperatures. When x grows from 0 to 0.30, the Curie temperature linearly grows from -10°C to +25°C, the dielectric permittivity ε_m in the Curie point T_C decreases from 18000 to 6800 and the phase transition becomes more diffused. The dielectric permittivity at room temperature is rather high and the temperature stability is improved. The system is of interest, because it can serve as a base for working out some ceramic materials for capacitors with low sintering temperature, which needs of no special atmosphere at burning.     

CeF3-modified LiNi1/3Co1/3Mn1/3O2 cathode material for high-voltage Li-ion batteries

A facile chemical deposition method has been adopted to prepare cerium fluoride (CeF₃) surface modified LiNi_1/3Co_1/3Mn_1/3O₂ as cathode material for lithium-ion batteries. Structure analyses reveal that the surface of LiNi_1/3Co_1/3Mn_1/3O₂ particles is uniformly coated by CeF₃. Electrochemical tests indicate that the optimal CeF₃ content is 1 wt%. The 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ can deliver a discharge capacity of 107.1 mA h g⁻¹ even at 5 C rate, while the pristine does only 57.3 mA h g⁻¹. Compared to the pristine, the 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ exhibits the greatly enhanced capacity and cycling stability in the voltage range of 3.0–4.5 V, which suggests that the CeF₃ coating has the positive effect on the high-voltage application of LiNi_1/3Co_1/3Mn_1/3O₂. According to the analyses from electrochemical impedance spectra, enhanced electrochemical performance is mainly because the stable CeF₃ coating layer can prevent the HF-containing electrolyte from continuously attacking the LiNi_1/3Co_1/3Mn_1/3O₂ cathode and retard the passivating layer growth on the cathode.     

Broadband dielectric spectroscopy of PbMg1/3Nb2/3O3–PbSc1/2Nb1/2O3 ceramics

Broadband dielectric spectroscopy results of various ordered and disordered (1 ? x)Pb(Mg_1/3Nb_2/3)O₃–(x)Pb(Sc_1/2Nb_1/2)O₃ (PMN–PSN) ceramics are investigated in the temperature range from 80 K to 300 K and frequency range from 20 Hz to 2 THz. Dielectric dispersion is very broad and in the ferroelectrics case (x = 1, 0.95) consists of two parts: low-frequency part caused by ferroelectric domains and higher frequency part caused by soft mode. The relaxational soft mode exhibits pronounced softening close to phase transition temperature, as it is typical for order–disorder phase transitions. By substituting Sc³⁺ by Mg²⁺ in PMN–PSN ceramics relaxation slows down, and for relaxors (x = 0.2) the most probable relaxation frequency decreases on cooling according to Vogel–Fulcher law.     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2研究进展

层状结构材料LiNi1/3Co1/3Mn1/3O2具有高比容量、高循环性能、低成本和环保等优点,有望取代LiCoO2成为新一代锂离子电池正极材料。在介绍LiNi1/3Co1/3Mn1/3O2的结构特点和电化学反应特性的基础上,对其主要合成方法进行了详细评述,总结了该正极材料的阴阳离子掺杂、复合离子掺杂以及表面包覆改性等技术,指出国内外目前锂离子电池材料研究中存在的问题和未来的发展方向。     

Local atomic characterization of LiCo1/3Ni1/3Mn1/3O2 cathode material

Co, Ni and Mn K-edge XAFS investigation of LiCo_1/3Ni_1/3Mn_1/3O₂ as alternative cathode material to commercially used LiCoO₂ in lithium rechargeable battery has been performed. Parameters of a local atomic structure such as radii of metal-oxygen and metal-metal coordination shells and disorder in those shells have been determined. It has been found that the radius of the first coordination shell (metal-oxygen) as well as a local disorder in the second shell (metal-metal) around each of the 3d-metals are in a good agreement with obtained for superlattice model of [√3 × √3] R30° type in triangular lattice of sites by first principle calculation. Other parameters of the local atomic structure around Co, Ni and Mn atoms do not provide evidence for presence of superstructure in LiCo_1/3Ni_1/3Mn_1/3O₂.     

不同铝源对LiNi1/3Co1/3Mn1/3O2材料的包覆改性研究

分别以纳米氧化铝、氢氧化铝及异丙醇铝为原料,采用液相浸渍法对LiNi1/3Co1/3Mn1/3O2材料进行氧化铝包覆,考察不同包覆源在LiNi1/3Co1/3Mn1/3O2材料表面进行氧化铝包覆后对材料电化学性能的影响。SEM及XRD结果显示,产物为层状α-NaFeO2结构,氧化铝均匀包覆在LiNi1/3Co1/3Mn1/3O2材料表面。充放电性能测试结果表明,在3种铝源中,以异丙醇铝为包覆源的材料性能最佳：在3.0~4.6 V的电压下,0.1 C倍率下首次放电比容量为196.1 mA·h/g, 1 C下循环50周后容量保持率为95.6%。     

Storage behavior of LiNi1/3Co1/3Mn1/3O2/artificial graphite Li-ion cells

A series of Li-ion cells containing LiNi_1/3Co_1/3Mn_1/3O₂ and artificial graphite as the active materials, have been stored at various temperatures from 0 to 70 °C. The 3-electrode impedance study shows that both the solid electrolyte interphase (SEI) film resistance and charge-transfer resistance of the negative electrode first decrease and then increase during storage at 70 °C, while both resistances for the positive electrode increase under this condition. The reversible capacity loss of the 3-electrode cell, which is possibly attributed to dissolution of SEI film, accounts for over half of the total capacity loss after 5 weeks of storage. Gases generated from the swelling aged cell at 60 °C are mainly attributed to the reduction of the electrolyte on the negative electrode. A further study on the side-reaction has been done on graphite electrodes and separators, indicating that SEI films may be rearranged and reformed on negative electrodes, and that some pores on the positive electrode side of separator are blocked due to the oxidation of electrolyte, resulting in poor Li-ion transfer and rise of the ohmic resistance during storage at elevated temperature. However, at 0 °C, this side-reaction is impeded.     

1:1 Ordered Domain Growth in Pb(Mg1/3Ta2/3)O3-La(Mg2/3Ta1/3)O3 Relaxor Ferroelectric Perovskites

Single-phase perovskite solid solutions are formed across the entire (1 - x )Pb(Mg_1/3Ta_2/3)O₃- x La(Mg_2/3Ta_1/3)O₃ (PLMT) pseudobinary system. Although as-sintered (1300°C, 3 h) samples with x lessthan equal to 0.1 adopt a phase-separated, "PMN-type" microstructure comprising small (2-3 nm) ordered domains dispersed in a disordered matrix, extensive domain growth and complete order can be induced by extended thermal annealing (1300°C, 24 h). These observations, and the alterations in the thermal stability and domain size across the system, can be interpreted using a charge-balanced random site model for the cation order. No evidence is found to support the space-charge models currently used to describe the cation ordering and properties of the corresponding niobate systems.     

Synthesis and characterization of LiNi1/3Mn1/3Co1/3O2 by wet-chemical method

A series of LiNi_1/3Mn_1/3Co_1/3O₂ samples with α-NaFeO₂ structure belonging to the D_3d⁵ space group were synthesized using tartaric acid as a chelating agent by wet-chemical method. Different acid to metal-ion ratios R have been used to investigate the effect of this parameter on the physical and electrochemical properties. We have characterized the reaction mechanism, the structure, and morphology of the powders by TGA, XRD, SEM and TEM imaging, completed by magnetic measurements, Raman scattering spectroscopy, and complex impedance experiments. We find that the LiNi_1/3Mn_1/3Co_1/3O₂ sintered at 900 °C for 15 h with an acid to metal-ion ratio R = 2 was the optimum condition for this synthesis. For this optimized sample, only 1.3% of nickel-ions occupied the 3b Wyckoff site of the lithium-ions sublattice. The electrochemical performance has been investigated using a coin-type cell containing Li metal as the anode. The electronic performance is correlated to the concentration of the Ni(3b) defects that increase the charge transfer resistance and reduce the lithium diffusion coefficient. The optimized cell delivered an initial discharge capacity of 172 mAh g⁻¹ in the cut-off voltage of 2.8-4.4 V, with a coulombic efficiency of 93.4%.