新型陶瓷连接材料(Pr0.5Nd0.5)0.7Ca0.3CrO3–δ–Sm0.1Gd0.1Ce0.8O1.9的制备与性能

采用络合燃烧法制备(Pr0.5Nd0.5)0.7Ca0.3CrO3–δ(PNCC)–Sm0.1Gd0.1Ce0.8O2–δ(SGDC)复合陶瓷连接材料。利用X射线衍射仪和扫描电子显微镜对烧结体的物相和微观结构进行了表征,采用四端探针法测量电导率。结果表明:PNCC和SGDC在高温烧结时具有稳定的物相和良好的化学相容性,SGDC掺杂量为5%(质量分数)的样品,在1400℃烧结5h,相对密度高达97.1%;700℃时,烧结陶瓷体在空气和氢气气氛中的电导率分别为47S/cm和4S/cm;室温至1000℃范围内,样品的热膨胀系数为10.4×10–6K–1,与中温电解质的热膨胀系数接近,说明SGDC掺杂的PNCC体系有望成为良好的中温固体氧化物燃料电池复合连接材料。     

Al2O3包覆LiNi0.5Mn0.5O2的电化学性能

通过溶胶-凝胶法在LiNi0.5Mn0.5O2表面包覆一层Al2O3,采用X射线衍射(XRD),扫描电镜(SEM),恒电流充放电和电化学阻抗谱(EIS)对材料的结构和形貌及电化学性能进行了研究。实验结果表明,经过包覆后,有效地抑制了电解液对正极材料的侵蚀,包覆量为1.0%(质量分数)放电容量略有提高,循环性能也得到明显改善。因此包覆是一种改善LiNi0.5Mn0.5O2材料的电化学性能的有效方法。     

Effect of SrZrO3 on phase structure and electrical properties of 0.974(K0.5Na0.5)NbO3–0.026Bi0.5K0.5TiO3 lead-free ceramics

(0.974−x)(K_0.5Na_0.5)NbO₃–0.026Bi_0.5K_0.5TiO₃–xSrZrO₃ lead-free piezoelectric ceramics have been prepared by the conventional solid state sintering method. Systematic investigation on the microstructure, crystalline structures as well as electrical properties of the ceramics was carried out. With the addition of SrZrO₃, the rhombohedral–orthorhombic phase transition temperature of the ceramics increases. Both the rhombohedral–orthorhombic and orthorhombic–tetragonal phase transitions of the ceramics were modified to be around room temperature when x~0.05, and as a result remarkably strong piezoelectricity has been obtained in 0.924(K_0.5Na_0.5)NbO₃–0.026Bi_0.5K_0.5TiO₃–0.05SrZrO₃ ternary system, whose piezoelectric parameters were d₃₃=324 pC/N and k_p=41%.     

High energy density capacitors based on 0.88BaTiO3–0.12Bi(Mg0.5, Ti0.5)O3/PbZrO3 multilayered thin films

Multilayered thin films consisting of both 0.88BaTiO₃–0.12Bi(Mg_0.5,Ti_0.5)O₃ ferroelectric layers and PbZrO₃ antiferroelectric layers were prepared by sol–gel method, exhibiting high dielectric permittivity, large polarization, high recoverable energy storage density and high energy storage efficiency. A maximum polarization of 93 μC/cm², recoverable energy storage density of 24.7 J/cm³ and energy storage efficiency of ~60% have been achieved at an electric field of 1050 kV/cm. Furthermore, the energy storage performance of the multilayered thin films was improved by modified layer-by-layer annealing process, where larger polarization (115 μC/cm²), higher recoverable energy storage density (33 J/cm³) and higher energy storage efficiency (~70%) were obtained.     

(1-x)Li0.05(K0.5Na0.5)0.95NbO3-x(Bi0.5Na0.5)TiO3无铅压电陶瓷的结构与电性能研究

采用固相反应法制备了(1-x)Li0.05(K0.5Na0.5)0.95NbO3-x(Bi0.5Na0.5)TiO3(LKNN-BNT)无铅压电陶瓷,研究了BNT的添加量x(0,0.005,0.01,0.02)对LKNN-BNT陶瓷的结构与电性能影响。X射线衍射(XRD)分析结果表明当x≤0.005时,陶瓷为正交钙钛矿结构,而当x≥0.01时,陶瓷则转变为四方钙钛矿结构,说明该陶瓷的多型相转变(PPT)区域为0.005相似文献   

Structure and electrical properties of Nd2O3-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 ceramics

Nd₂O₃ doped 0.82Bi_0.5Na_0.5TiO₃–0.18Bi_0.5K_0.5TiO₃ (abbreviated to BNKT) binary lead-free piezoelectric ceramics were synthesized by the conventional mixed-oxide method. The results show that the BNKT ceramics with 0–0.15 wt.% Nd₂O₃ doping possesses a single perovskite phase with rhombohedral structure. The grain size of BNKT decreased with the addition of Nd₂O₃ dopant. The temperature dependence of the dielectric constant ?_r revealed that there were two-phase transitions from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric. A diffuse character was proved by linear fitting of the modified Curie–Weiss law. At room temperature, the specimens containing 0.0125 wt.% Nd₂O₃ with homogeneous microstructure presented excellent electrical properties: the piezoelectric constant d₃₃ = 134 pC/N, the electromechanical coupling factor K_p = 0.27, and the dielectric constant ?_r = 925 (1 kHz).     

水热法合成Ce0.9Gd0.1O1.95及其光催化性质研究

采用水热法合成了花状Ce0.9Gd0.1O1.95纳米粉,通过X射线衍射、红外光谱、场发射扫描电子显微镜测试手段对产物进行了表征,探讨了其生长机制,以亚甲基蓝的光降解为模型反应,研究其光催化性能。结果表明,以甲酸为介质,110℃的水热条件下合成的纳米Ce0.9Gd0.1O1.95颗粒经800℃煅烧后具有萤石结构,平均晶粒尺寸为21.6 nm,花状形貌;由于Gd3+的掺杂,纳米Ce0.9Gd0.1O1.95对亚甲基蓝紫外光催化性能强于未掺杂的CeO2。该合成方法简单易行,对纳米Ce0.9Gd0.1O1.95的形貌控制起到了启示作用,所得的花状纳米Ce0.9Gd0.1O1.95在光催化领域有着重要应用价值。     

Microstructure and electrical properties of (Na0.5K0.5)1−2xMgxNbO3–Bi0.5Na0.5TiO3 lead-free piezoelectric ceramics

0.975[(Na_0.5K_0.5)_1−2xMg_xNbO₃]–0.025(Bi_0.5Na_0.5TiO₃) (KNMN–BNT, x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) lead-free piezoelectric ceramics were fabricated by the conventional solid-state sintering method. The dependence of Mg content on the microstructure and electrical properties of the ceramics is investigated. The X-ray diffraction (XRD) analysis revealed that an appropriate amount of Mg diffused into the KNN–BNT lattice to form a stable solid solution, the ceramics possessed a pure perovskite structure, and a morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was observed with the composition of 0.02≤x≤0.05. The orthorhombic–tetragonal transition temperature (T_O–T) is less than 95 °C and the Curie temperature (T_c) is almost unchanged (~360 °C) with the increase of MgO content. The ceramics with x=0.02 showed enhanced piezoelectric and ferroelectric properties because of close proximity to the MPB, i.e., d₃₃~210 pC/N, k_p~0.41, 2E_c~22.4 kV/cm and 2P_r~39.2 μC/cm². Moreover, the dielectric properties exhibited optimal effects with x=0.02, that is ε_r~637 and tan δ~0.09. These results indicate that the introduction of MgO is an effective method to improve the density as well as the electrical properties and the temperature stability of the KNN–BNT ceramics. As a result, the KNMN–BNT ceramic is a promising candidate for lead-free piezoelectric materials.     

添加Y2O3对CaO-MgO-SiO2体系中CMS的影响

为了提高镁质耐火材料的高温性能,以分析纯化学试剂MgO、CaO、SiO₂、Y₂O₃等为主要原料,研究了添加Y₂O₃对CaO-MgO-SiO₂体系中钙镁橄榄石(CMS)的生成和转化的影响,以及转化生成物Ca₄Y₆O(SiO₄)₆的耐火度。结果表明：1)Y₂O₃的添加不仅能够显著减少CaO-MgO-SiO₂体系中低熔点相CMS的生成量,而且能够从CMS中捕获CaO和SiO₂使CMS转化为高熔点相Ca₄Y₆O(SiO₄)₆、MgO和Y₂Si₂O₇,有利于提高镁质材料的高温性能。2)Ca₄Y₆O(...     

Y2O3掺杂TiO2催化超声降解苯胺的研究

选取苯胺为降解目标物,研究了用实验室合成的氧化钇掺杂二氧化钛为催化剂存在下的超声反应,重点考察了超声时间长短、氧化钇的掺杂量、二氧化钛的添加量、溶液初始浓度、溶液pH值对苯胺降解率的影响。实验结果表明,在溶液pH 2.0、苯胺质量浓度为20mg/L、溶液用量50mL、氧化钇掺杂比为0.1%、催化剂用量为0.02g的条件下,用输出功率5.0 W/cm2和频率25kHz的超声波照射80min,苯胺降解率可达93.94%。     

Ca0.95-xCu0.05(Na0.5Bi0.5)xMoO4微波介质陶瓷的制备及性能

随着当下5G和6G技术的高速发展,开发出具有适中的介电常数,较高的品质因数,接近0的谐振频率温度系数的陶瓷已是当下研究的重点。通过固相法制备Ca_0.95–xCu_0.05(Na_0.5B_i0.5)_xMo O₄微波介质陶瓷,研究烧结温度和组分变化对陶瓷微波介电性能的影响。当烧结温度为640℃、x为0.5时综合微波介电性能较好,此时陶瓷的ε_r=15.8,Q_f=21 361 GHz,τ_f=?3.8×10^?6/℃。通过X射线衍射仪、Raman光谱仪、扫描电子显微镜研究了微波介电性能变化的机理。Ca_0.45Cu_0.05(Na_0.5Bi_0.5)_0.5Mo O₄陶瓷与Al电极共烧结果显示有较好的相容性,表明Ca_0.95?xCu_...     

Excess conductivity in Cu0.5Tl0.5Ba2(Ca2−yMgy)(Cu0.5Zn2.5)O10−δ superconductor

Synthesis and characterization of Cu_0.5Tl_0.5Ba₂(Ca_2−yMg_y)(Cu_0.5Zn_2.5)O_10−δ (y=0, 1.0, and 1.5) superconductor with 0%, 50%, and 75% Mg-doping at the Ca sites are reported. The samples were synthesized by solid-state reaction and characterized by X-ray diffraction (XRD), dc-resistivity (ρ) and fluctuation induced conductivity (FIC) analysis. The zero resistivity critical temperature {T_c(R=0)} was decreased with the increase of Mg-doping at Ca sites. The microscopic parameters such as the cross-over temperature (T_o), zero temperature coherence length {ξ_c(0)} and interlayer coupling (J) were deduced from FIC analysis. According to Aslamazov Larkin equations, a distinct cross-over temperature (T_o1) from three-dimensional (3D) to two-dimensional (2D) fluctuation induced conductivity regions was observed in all samples. Another cross-over temperature (T_o2) from 2D to zero-dimensional (0D) fluctuations was also witnessed. FIC analysis revealed the deterioration of superconductivity with increased Mg-content.     

Co2O3掺杂对(Na0.8K0.2)0.5Bi0.5TiO3陶瓷结构与电性能的影响

采用传统固相法制备了(Na0.8K0.2)0.5Bi0.5TiO3+xmol%Co3+(BNKT-xCo,x=0-8)无铅压电陶瓷,研究了Co2O3掺杂对BNKT陶瓷的显微结构与电学性能的影响。研究表明:适量的Co2O3掺杂促进了晶粒生长,纯BNKT陶瓷样品在介电温谱上有2个介电反常峰Td和Tm,Co2O3掺杂后使所有陶瓷样品的第一个介电反常峰Td消失,表明Co3+抑制铁电-反铁电相变。室温下样品的介电、铁电和压电性能表明Co2O3起硬性掺杂效应。当x=7时陶瓷样品电性能最佳,其中机械品质因子Qm=498,介电损耗tanδ=2.3%(1kHz),压电常数d33=103pC/N,平面机电耦合系数kp=27%。     

Sr0.5Zr2(PO4)3陶瓷的力学性能研究

用共沉淀法和低分子有机溶剂分散获得SZP粉体,经干压成型和烧结得到SZP陶瓷.研究了其力学性能与烧结温度烧结时间和添加剂用量的关系.最佳工艺条件为添加MgO6wt%,1300℃或ZnO3wt%,1200℃均烧结1.5小时,SZP陶瓷的抗压强度分别可达244.0MPa和226.2MPa.     

Effect of the Nb2O5 content on electrical properties of lead-free BaTiO3–Bi0.5Na0.5TiO3 ceramics

(1−x)BaTiO₃–xBi_0.5Na_0.5TiO₃ (BT–BNT) ceramics were prepared by the solid-state reaction method. With an increase of BNT content, both the Curie temperature and the room temperature resistivity increased. At 1 mol% BNT addition, the sample was not semiconducting, due to Bi₂O₃ volatilization resulting from the decomposition of pre-calcined BNT during sintering. Appropriate extra Nb₂O₅ doping in the raw materials could offset Bi₂O₃ volatilization and neutralize the redundant acceptor Na⁺ ions. When the extra Nb₂O₅ content was 0.6 mg, the sample room-temperature resistivity was 6.3×10³ Ω cm, with the Curie point about 135 °C and a high PTC effect of ∼3 orders of magnitude.     

NaNbO3–CaZrO3–Bi0.5Na0.5TiO3三元系陶瓷的相结构与储能性能

铌酸钠(NaNbO₃)无铅陶瓷由于其无毒和出色的储能性能，在脉冲功率电容器领域吸引了越来越多的关注。然而，由于较大的有效储能密度(W_rec)和高的储能效率(η)不能同时实现，限制了其商业化。通过构建局域随机场，增加弛豫特性来提高储能性能的策略。采用传统固相法制备了(1–x)(0.96Na Nb O₃–0.04CaZrO₃)–x Bi_0.5Na_0.5TiO₃ (x=0.05、0.10、0.15、0.20)反铁电储能陶瓷，研究了不同含量Bi_0.5Na_0.5TiO₃对0.96Na Nb O₃–0.04CaZrO₃陶瓷的相结构、微观形貌、介电性能和储能特性的影响。结果表明：随着Bi_0.5Na_0.5TiO₃含量的增加，(1–x)(0.96NaNbO₃...     

Magnetic and magnetotransport properties of La1−xSrxMn0.5Сo0.5O3 perovskites

La_1?xSr_xMn_0.5Сo_0.5O₃ (x ≤ 0.75) perovskites have been studied as a function of temperature by neutron powder diffraction (NPD), magnetization and magnetoresistance measurements. The NPD data show that x = 0.15 and 0.5 compounds are stoichiometric, so the Sr²⁺ doping transforms Co²⁺ ions into the Co³⁺ ones, whereas manganese ions remain in the 4+ oxidation state as in the parent ferromagnetic compound ${\mathrm{LaCo}}_{\mathrm{0.5}}^{\mathrm{2}+}{\mathrm{Mn}}_{\mathrm{0.5}}^{\mathrm{4}+}{\mathrm{O}}_{\mathrm{3}}$. The magnetization data show a decrease in the Curie temperature from 215 K for the compound with x = 0 down to 147 K for the compound with x = 0.05. The compounds with x > 0.15 show an increase in T_C up to 260 K (x = 0.75) in spite of a gradual decrease of the spontaneous magnetization. The stoichiometric compound x = 0.5 demonstrates a sharp ferromagnet-paramagnet transition with T_C = 250 K. However, there is no visible coherent magnetic contribution to the NPD patterns. All compounds are semiconductors and exhibit large magnetoresistance gradually increasing with decrease of temperature. The magnetic data have been interpreted assuming that the Co³⁺ ions are in high spin state, however, there is a fraction of cobalt ions in low spin state. It is suggested that the superexchange interaction between Co³⁺ ions in the high spin state and Mn⁴⁺ ions is ferromagnetic and that the ferromagnetism of the compounds with x > 0.5 and high T_C is associated with positive exchange interactions between Co³⁺ being in high spin state and Mn⁴⁺ ions distributed within the short range regions. Based on the NPD results and magnetization data the magnetic phase diagram has been constructed.     

Y2O3和CeO2对镁砂烧结性能及显微结构的影响

以菱镁石于950℃制得的轻烧MgO粉(≤0.088 mm)为主要原料,分别加入质量分数为1%、2%、3%、4%的Y2O3和CeO2混匀,压制成型后于1 600℃煅烧3 h,冷却后测其体积密度和线收缩率,并利用XRD、SEM、EDS分析试样的物相组成及显微结构,以研究Y2O3和CeO2对镁砂烧结性能和显微结构的影响。结果表明:1)引入Y2O3和CeO2均有利于镁砂的烧结致密化,镁砂试样的体积密度和烧后线收缩率随其加入量的增加而增大;在加入量相同的情况下,加入Y2O3对镁砂的促烧结作用比加入CeO2的更明显。2)引入的Y2O3和CeO2都有部分固溶于方镁石晶体内,使MgO晶格发生畸变,有利于MgO晶粒发育良好,晶粒长大,晶界明显;Y2O3能与镁砂中的CaO、SiO2形成钇硅酸盐相分布在晶粒之间,而部分CeO2以游离形式存在于晶粒之间。3)与引入CeO2的试样相比,引入Y2O3的试样中气孔更加集中,晶界更加清晰,MgO晶粒尺寸较大,这是由于Y2O3和CeO2的性质差异造成稀土离子参与固溶体粒子取代程度不同的缘故。     

铁钕掺杂K0.5Na0.5NbO3陶瓷的压电介电性能

采用传统陶瓷制备技术制备了新型的K0.5Na0.5NbO3+0.2%molFe2O3+x%molNd2O3压电陶瓷,研究了该体系陶瓷的压电性能及介电性能。研究结果表明,在烧结温度为1120℃、4 h时,该体系陶瓷均具有相对较好的电学性能,并在x为0.2时性能最佳,其压电常数d33为125pC/N,机电耦合系数Kp为37%,机械品质因素Qm为155,介电常数εr为561,介质损耗tanδ为0.08。