(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3多铁性材料的有序结构及磁性能

以无机盐为前驱体,利用溶胶-凝胶法固溶合成了(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3多铁性固溶体.XRD分析表明,在0≤x≤1.0的掺杂范围内,700℃煅烧所得产物都具有钙钛矿结构;x=0时得到的纯Pb(Fe2/3W1/3)O3为长程无序结构,x=1.0时可获得完全有序的纯Pb(Mg1/2W1/2)O3相,其单胞为Pb(Fe2/3W1/3)O3单胞的2倍;当0相似文献   

PDP铝酸盐绿色荧光粉基质BaAl12O19的单相合成研究

研究了Ba含量及掺杂Mg、Sr对BaAl12O19单相合成的影响.研究结果表明Ba1+xAl12O19+x中Ba含量在1.1～1.2时,α-Al2O3和BaAl2O4相残余难以被XRD检出;Mg的掺入可以优化BaAl12O19的结晶,Ba11MgyAl12-yO191-y/2中Mg的含量在0.8～1.1时可以获得单相;掺Sr使部分衍射峰位置向高角度方向漂移,Ba1 2-zSrzMg0 8Al1.2O18.8中Sr的掺入量为0.4左右时合成出更为纯净的单相.     

MnO2对Ba(Mg1/3Nb2/3)O3微观结构和微波介电性能的影响

研究了MnO2助烧剂对Ba(Mg1/3Nb2/3)O3陶瓷的微观结构和微波介电性能.MnO2可以有效地使Ba(Mg1/3Nb2/3)O3陶瓷的致密化温度由1550℃降低到1400℃左右.随MnO2掺量的增加,Ba(Mg1/3Nb2/3)O3陶瓷的12超晶格衍射峰的强度减弱,但是没有第二相出现.1400℃烧结4h陶瓷的晶粒尺寸在1.5μm左右.MnO2的掺入改善了Ba(Mg1/3Nb2/3)O3陶瓷的微波介电性能,MnO2掺量为1%mol的Ba(Mg1/3Nb2/3)O3陶瓷具有最好的微波介电性能εr≈31.5,Qf=68000,τf=3.11×10-5/℃,这可归功于陶瓷具有相当高的相对密度.     

Ba置换改性(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷结构与微波介电性能的研究

研究了Ba置换改性对Ca [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷微观结构与介电性能的影响.通过XRD与SEM分析发现,当x=0.15,(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3形成了正交晶系钙钛矿结构的单相固溶体;当x=0.20～0.80时,改性陶瓷为正交与六方钙钛矿结构的两相复合固溶体;当x=0.85 时,所形成(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷为六方钙钛矿结构的单相固溶体.(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3系陶瓷微波介电性能的变化与Ba在材料内部的分布状态密切相关,与基材CMNT陶瓷相比:当x=0.15时,陶瓷的介电常数提高,介电损耗降低,谐振频率温度系数向负方向移动:εr=55,Qf值=32000GHz(6.5GHz下),τf=-36.82ppm/℃;当x=0.20～0.80间变化时,(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3两相复合陶瓷的微波介电性能由于复合效应而表现出连续变化的规律:εr= 45～33 ,Qf值= 30500～40200GHz(6.3GHz～7.6GHz下),τf = -17.7～12.52ppm/℃;当x=0.85时,单相钙钛矿固溶体(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3获得良好的微波介电性能:εr=31,Qf值达到44000GHz(8.5GHz下),τf=10.81ppm/℃.     

液相包裹法制备Pb(Mg1/3Nb2/3)O3-CoFe2O4磁电耦合材料

以无机盐Nb2O5、Mg(NO3)2、Pb(NO3)4、Co(NO3)2、Fe2(NO3)3为原料,柠檬酸和EDTA为络合剂,分别制备了Nb5+、Mg2+、Pb2+、Co2+、Fe3+等离子的络合溶液。采用络合法制备了铌酸镁-铁酸钴先驱体(MgNb2O6-CoFe2O4,简称MN-CFO)。此先驱体在1000℃煅烧1h后,得到纯净的MgNb2O6-CoFe2O4固溶体。采用液相包裹法制备了铌镁酸铅-铁酸钴(Pb(Mg1/3Nb2/3)O3-CoFe2O4)先驱体,在1000℃煅烧1h,Pb(Mg1/3Nb2/3)O3-CoFe2O4先驱体分解为具有铁电相Pb(Mg1/3Nb2/3)O3和铁磁相CoFe2O4的复相组织。研究了10%过量的PbO对煅烧过程中烧绿石相向铁电相的转变作用,并在700℃煅烧5h条件下制备了不含烧绿石相的Pb(Mg1/3Nb2/3)O3-CoFe2O4固溶体。     

(Ba1-xSrx)La4Ti4O15（x=0.8～0.95）陶瓷的微结构及微波介电性能研究

采用固相反应法制备了(Ba1-xSrx)La4Ti4O15(x=0.8~0.95)复合体系微波介质陶瓷,并对其进行物相组成、晶体结构分析以及微波介电性能的研究.研究结果表明,(Ba1-xSrx)La4Ti4O15陶瓷主晶相为SrLa4Ti4O15,并伴随有第二相SrLa8Ti9O15.SEM观察表明,Ba0.2Sr0.8La4Ti4O15陶瓷内部微观结构致密,晶粒尺寸在10~20μm之间,晶界清晰.随着x值逐渐增大,(Ba1-xSrx)La4Ti4O15陶瓷中晶粒形态发生变化,气孔增多.在x=0.8时,(Ba1-xSrx)La4Ti4O15陶瓷具有优良的微波介电性能,即εr=40.86,Q×f≈62806 GHz,τf=20×10 6/℃.随着Ba2+的含量逐渐增加,该陶瓷的介电常数εr单调上升,品质因子Q×f值增加,说明适量的Ba2+替代Sr2+能改善陶瓷的微波介电性能.     

(Mg1-xSrx)2Al4Si5O18陶瓷的显微结构与微波介电性能研究

采用固相烧结反应法制备(Mg1-xSrx)2Al4Si5O18陶瓷.Sr掺杂促进低温相β-Mg2Al4Si5O18向高温相α-Mg2Al4Si5O18转变,并拓宽了(Mg1-xSrx)2Al4Si5O18陶瓷的致密化烧结温度范围.X射线衍射结果表明在0≤x<0.2范围内,(Mg1-xSrx)2Al4Si5O18陶瓷以(Mg,Sr)2Al4Si5O18堇青石固溶体形式存在;在0.6相似文献   

Li_(1+x)Ti_(2-x)Cr_xP_3O_(12)系统的相关系与电性

研究了 Li_(1+x)Ti_(2-x)Cr_xP_3O_(12)系统的相组成与电性的关系。结果表明,Cr~(3+)能取代 LiTi_2P_3O_(12)中的Ti~(4+)生成固溶体,直至 x=0.8。在固溶体范围内,电导率随 x 的增加不断升高,至 x=0.8时达到极大。此时在室温和300℃的电导率分别为2.4×10~(-4)和4.8×10~(-2)S/cm,电子迁移数在10~(-4)数量级,分解电压为1.8V。对所得结果从结晶化学角度进行了讨论。     

熔盐合成BaFe12O19六角铁氧体及磁性能研究

以Fe2O3、BaCO3为原料,采用熔盐法合成了BaFe12O19(BaM)六角铁氧体,研究了煅烧温度、反应时间、熔盐添加量R及Fe3+/Ba2+摩尔比对产物物相、显微结构及磁性能的影响.结果表明,熔盐合成BaM的反应温度低于750℃,中间产物为BaFe2O4及BaFe4O7.Fe3+/Ba2+摩尔比在10～11.5可得BaM单相.熔盐添加量R为1～3时,所制BaM颗粒为规则六角片状.Fe3+/Ba2+摩尔比为11.5,煅烧温度为1000℃时制得的BaM的比饱和磁化强度为71.9A.m2/kg,接近其理论值72A.m2/kg.     

一种新型湿化学方法合成Ba(Mg1/3Ta2/3)O3纳米粉末的研究

介绍了一种工艺简便且成本较低的Ba(Mg1/3Ta2/3)O3(BMT)纳米粉末的湿化学制备方法.实验过程以Ta2O5作为起始物,通过热碱反应与钽离子浓度控制法合成Ta2O5@nH2O胶体,然后与Ba、Mg醋酸盐按化学计量比混合,经热处理制得BMT纳米粉末.实验结果表明该方法制备BMT粉体所需的合成温度仅为800℃,比传统固相反应法合成温度降低400℃左右,平均粒径仅为70nm.此外所制得的纳米陶瓷材料具有较佳的低温烧结性能和微波介电特性,比目前报道的醇盐系湿化学制备技术更具有实用性.     

Synthesis and characterization of Mg3Cr2Si3O12-Fe3Cr2Si3O12 garnet solid solutions

Homogeneous garnet Fe₃Cr₂Si₃O₁₂ and its solid solutions with garnet Mg₃Cr₂Si₃O₁₂ (four intermediate samples) were synthesized at high pressure. Garnet Mg₃Cr₂Si₃O₁₂ was not synthesized in pure form. The sample contained traces of the two phases, MgSiO₃ and Cr₂O₃. The products were investigated by means of X-ray powder diffraction and differential scanning calorimetry. Molar volumes of the solid solutions as a function of composition fit linear regression with an accuracy of 0.2%. No difference in heat capacity within the limits of experimental error was detected. In thermodynamic evaluations, the garnet solid solutions Fe₃Cr₂Si₃O₁₂-Mg₃Cr₂Si₃O₁₂ may be treated as ideal solid solutions.     

Thermal expansion studies of Gd2Mo3O12 and Gd2W3O12

Simultaneous thermogravimetric/differential thermal analysis of Gd₂Mo₃O₁₂ showed an irreversible phase transition at 1178 K where as Gd₂W₃O₁₂ showed reversible phase transition at 1433 K, which were confirmed by powder X-ray diffraction. The thermal expansion behavior of α-Gd₂Mo₃O₁₂ (room temperature phase), β-Gd₂Mo₃O₁₂ (phase obtained by heating Gd₂Mo₃O₁₂ at 1223 K) and Gd₂W₃O₁₂ have been investigated using high temperature X-ray diffractometer. The cell volume of α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂, fit into polynomial expression with respect to temperature, showed positive thermal expansion up to 1073, 1173 and 1173 K, respectively. The average volume expansion coefficients for α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂ are 39.52 × 10⁻⁶, 21.23 × 10⁻⁶ and 37.96 × 10⁻⁶ K⁻¹, respectively.     

Elastic modulus and hardness of CaTiO3, CaCu3Ti4O12 and CaTiO3/CaCu3Ti4O12 mixture

Three ceramic systems, CaTiO₃ (CTO), CaCu₃Ti₄O₁₂ (CCTO) and intermediate nonstoichiometric CaTiO₃/CaCu₃Ti₄O₁₂ mixtures (CTO.CCTO), were investigated and characterized. The ceramics were sintered at 1100 °C for 180 min. The surface morphology and structures were investigated by XRD and SEM. Elastic modulus and hardness of the surfaces were studied by instrumented indentation. It was observed that CCTO presented the higher mechanical properties (E = 256 GPa, hardness = 10.6 GPa), while CTO/CCTO mixture showed intermediate properties between CTO and CCTO.     

The crystal structure of eulytite Pb3BiV3O12

The crystal structure of Pb₃BiV₃O₁₂ was solved using single-crystal X-ray diffraction technique. The compound crystallizes in the cubic system (No. 220) with eulytite structure with a = 10.7490(7) Å, V = 1241.95(14) Å³ and Z = 4. The final R₁ value of 0.0198 (wR₂=0.0384) was achieved for 359 independent reflections during the structure refinement. The Pb²⁺ and Bi³⁺ cations occupy the special position (16c) while the oxygen anions occupy the general position (48e) in the crystal structure. Unlike many other eulytite compounds, all the crystallographic positions are fully occupied. The structure consists of edge-shared Pb/Bi octahedra linked at the corners to independent [VO₄]³⁻ tetrahedra units, generating a eulytite-type network in the crystal lattice.     

Growth of Ca3Fe2Ge3O12 and Ca3Fe(Al,Cr) Ge3O12 garnets in molten bismuth germanate glasses

Additions of Fe₂O₃ to CaO·Bi₂O₃·2 GeO₂ cause Ca₃Fe₂Ge₃O₁₂ garnets to precipitate from the resultant melt at 1250°C. Garnets with the composition Ca₃Fe(Al, Cr) Ge₃O₁₂ are also precipitated by adding either $\text{Al}{}_2\text{O}{}_3\text{Fe}{}_2\text{O}{}_3$ or $\text{Cr}{}_2\text{O}{}_3\text{Fe}{}_2\text{O}{}_3$ mixtures. The well-formed crystals range from several to 100 μm in size and are obtained in 50 to 70% yields at $\text{Fe}\text{Bi}\text{= 0.4}$. Additions of Fe₂O₃ (up to $\text{Fe}\text{Bi}\text{= 1.0}$) to compositions containing ZnO, CdO, SrO, and BaO yield only dark glasses. The physical properties of these glasses suggest that Fe(III), in contrast to AL(III) & Ga(III), prefers octahedral coordination.     

Time-resolved spectroscopy of intrinsic luminescence of Y3Ga5O12 and (LaLu)3Lu2Ga3O12 single crystals

The nature of intrinsic luminescence of Y₃Ga₅O₁₂ (YGG) and (LaLu)₃Lu₂Ga₃O₁₂ (LLGG) single crystals grown from a melt was determined. In the case of a YGG single crystal containing Y_Ga antisite defects with a concentration of 0.25–0.275 at.% the intrinsic luminescence was considered as a superposition of luminescence of self-trapped excitons (STE), luminescence of excitons localized near antisite defects (LE(AD) centers) and luminescence caused by a recombination of an electron with a hole captured at Y_Ga antisite defects. Due to a large (2–3%) concentration of Lu_La antisite defects in LLGG single crystals the intrinsic luminescence was a superposition mainly of the LE(AD) center emission and the recombination luminescence of Lu_La antisite defects. The energy structure of the mentioned centers in YGG and LGGG hosts was determined from the excitation spectra of their luminescence under excitation by synchrotron radiation in the range of the fundamental absorption edge of these garnets.     

Ag/Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si结构铁电薄膜制备及其铁电性能的研究

利用溶胶-凝胶(sol-gel)方法,在硅基底上制备了Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si铁电薄膜,其中Bi4Ti3O12作为缓冲层.用XRD方法分析了该结构铁电薄膜的物相结构;用扫描电镜对薄膜样品进行表面形貌观察;并且对该结构的铁电性能进行了研究.     

Thermodynamic properties of DyFeO3 and Dy3Fe5O12

A solid state electrochemical technique was employed to study the dissociation oxygen partial pressures of DyFeO₃ and Dy₃Fe₅O₁₂ at elevated temperatures. The standard enthalpies ΔH^o_f and entropies ΔS^o_f of formation were obtained to be - 1349.7 kJ/mol and - 253.2 J/mol·K for DyFeO₃ in the temperature range from 1173 to 1473 K, and - 4879.5 kJ/mol and - 1011.6 J/mol·K for Dy₃Fe₅O₁₂ in the temperature range from 1173 to 1523 K, respectively.     

NMR study of ionic motions in both Tl2Zr3OF12 and Rb2Zr3OF12 oxyfluorides

The ionic transport properties of two members, namely Tl₂Zr₃OF₁₂ and Rb₂Zr₃OF₁₂ of a new series of oxyfluorides with formula M₂M′₃OF₁₂ (M = Rb, T1, NH₄; M′ = Zr, Hf) have been investigated using pulse NMR techniques and ionic conductivity measurements. The obtained results show that on the low temperature range fluorine is responsible for the conductivity of these materials while at temperatures higher than 450K the thallium ions probably contribute also to the conductivity. The extent of substitution of trivalent ions such as In³⁺ and Y³⁺ for Zr⁴⁺ has been determined as well as the effect of these substitutions on the ionic conductivity.     

热键合制作Yb:Y3Al5O12/Y3Al5O12复合晶体

采用热键合技术制备了Yb:Y3Al5O12/Y3Al5O12(Yb:YAG/YAG)复合晶体,对复合晶体进行了结构表征和键合质量检测.利用光学显微镜和扫描电镜观察了复合晶体横截面的形貌;在偏光显微镜下观察键合区域的应力,利用干涉条纹来表征复合晶体的光学均匀性;通过红外透过光谱的测量来检测复合晶体的键合质量.实验结果表明:热键合技术制备的Yb:YAG/YAG复合晶体键合界面处无界面缺陷,不存在复合界面空间过渡层,光学均匀性良好.