ZBL低温助烧Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Nd_(0.5)TiO_3微波介质陶瓷

通过XRD衍射仪、SEM扫描电镜表征掺杂ZnO-B_2O_3-Li_2O_3(ZBL)低软化点玻璃助烧剂的Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Nd_(0.5)TiO_3(CLLNT)陶瓷样品的物相组成及结构,研究ZBL玻璃的掺杂量对CLLNT样品烧结性能及微波介电性能的影响。研究表明:加入助烧剂(ZBL)后,CLLNT陶瓷的烧结温度降低至950℃;添加9 wt%ZBL玻璃的CLLNT陶瓷在950℃烧结3h,能够获得较好的介电性能:ε_r=82,tanδ=0.0026,τ_f=16 ppm/℃(1 MHz)。     

(1-x)Ca_(15/16)Sr_(1/16)TiO_3-xLi_(1/2)Nd_(1/2)TiO_3陶瓷的相组成、显微结构及微波介电性能

采用传统固相法合成了(1-x)Ca_(15/16)Sr_(1/16)TiO_3-xLi_(1/2)Nd_(1/2)TiO_3(CST-LNT)系列微波介质陶瓷材料,研究了该系列材料的物相组成、显微结构及微波介电性能。XRD分析结果表明所有样品均为钙钛矿结构,无二次相出现。随着Li_(1/2)Nd_(1/2)TiO_3的加入,陶瓷平均晶粒尺寸下降,表明Li_(1/2)Nd_(1/2)TiO_3会抑制晶粒生长。随着x的增加,介电常数下降,频率温度系数向负方向移动。当x=0.85时,1250℃保温4 h可以得到优良的微波介电性能:ε_r=125.4,Q×f=2230GHz,τ_f=+14.4 ppm/℃。     

Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Sm_(0.5)TiO_3复合微波陶瓷的介电性能

采用传统固相合成法制备了xCa0.6La0.8/3TiO3-(1-x)(Li0.5Sm0.5)TiO3(CLT-LST)系列微波介质陶瓷材料,研究了该系列微波介质陶瓷的物相结构、表面形貌、介电性能。实验发现:随着Ca0.6La0.8/3TiO3含量的增多,CLT-LST样品XRD峰轻微左移。陶瓷组成对微波介电性能影响显著,复合体系CLT-LST的微波介电性能随着x值不同而连续变化:当x从0.2上升到0.6时,介电常数(εr)逐步增大,在x=(0.4~0.6),εr变化趋于稳定,达到较佳值;品质因数(Q·f)则先减小后增大再迅速减小;谐振频率温度系数(τf)逐渐从负值向正值方向移动。当复合体系组成为0.4Ca0.6La0.8/3TiO3-0.6(Li0.5Sm0.5)TiO3时,在1 250℃烧结4h所得到的微波介电性能较佳,εr=125;Q·f=2 680GHz;τf=7.0×106/℃。     

Ca_(0.7)Bi_(0.15)Na_(0.15)TiO_3-NdAlO_3复合陶瓷微波介电性能研究

通过传统固相烧结法制备了(1-x)(Ca_(0.7)Bi_(0.15)Na_(0.15)TiO_3)-xNdAlO_3(CBNT-xNA,x=0.3, 0.35, 0.4, 0.5)陶瓷,并采用X射线衍射仪、扫描电子显微镜和网络矢量分析仪分别对其晶体结构、表面形貌及微波介电性能进行了系统研究。结果表明:NdAlO_3添加可以有效增加复合陶瓷的晶粒尺寸;CBNT-NA复合陶瓷主要为钙钛矿结构,并伴随有CaAl_(12)O_(19)和Ti_6O_(11)第二相产生;CBNT-0.35NA陶瓷的微波介电性能性能最佳,ε_r=52.1,Q×f=5862 GHz,τ_f=11.5×10~(-6)/℃。     

ZnSO_4溶液包覆Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Nd_(0.5)TiO_3微波介电陶瓷的研究

采用固相合成Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Nd_(0.5)TiO_3(CLT-LNT)微波介质陶瓷基体粉体,以ZnSO_4溶液为先驱体引入ZnO来降低该陶瓷的烧结温度,这种液相引入助烧剂的方法不仅减少了烧结助剂的用量,而且改善了陶瓷材料的介电性能。研究表明:掺入ZnO的CLT-LNT陶瓷在980℃烧结时的介电常数(ε_r)和介电损耗(tanδ)随着ZnSO_4溶液浓度的增大先增大后略有减小。当ZnSO_4溶液的浓度为0.32 mol/L时,CLT-LNT陶瓷在980℃烧结3 h获得较好的介电性能:ε_r=102,tanδ=0.0027,τ_f=-3×10~(-6)/℃。     

Nd~(3+)掺Na_(0.25)K_(0.25)Bi_(2.5)Nb_2O_9压电陶瓷的结构与性能

采用固相法制备Na_(0.25)K_(0.25)Bi_(2.5–x)Nd_xNb_2O_9(NKBN–xNd~(3+),0≤x≤0.40,x为摩尔分数)铋层状无铅压电陶瓷,研究了不同Nd~(3+)掺杂量对NKBN–x Nd陶瓷显微结构、电学性能的影响及NKBN–0.20Nd~(3+)陶瓷高温下的电导行为。结果表明:所有样品均为单一的铋层状结构;当Nd~(3+)的掺杂量x为0.02时,样品的晶粒尺寸减小并趋于均匀,致密度提高;适量的Nd~(3+)掺杂能降低样品的介电损耗,提高NKBN陶瓷的压电常数d33。NKBN–0.20Nd~(3+)陶瓷样品的电学性能最佳:压电常数d_(33)=24 p C/N,机械品质因数Q_m=2 449,tanδ=0.40%,2P_r=1.11μC/cm~2。NKBN–0.20Nd~(3+)样品的阻抗谱表明:在高温区域陶瓷的晶粒对电传导起主要作用,当温度高于600℃时,样品主要表现为本征电导,NKBN–0.20Nd~(3+)和NKBN的电导活化能分别为1.85和1.64 e V。     

Fe_2O_3掺杂BaZr_(0.1)Ti_(0.9)O_3陶瓷介电性能的研究

采用传统固相法分别于1250℃、1280℃、1300℃、1330℃下制备了BaZr_(0.1)Ti_(0.9)O_3+xmol%Fe_2O_3(0≤x≤1.25)陶瓷样品。XRD结果表明,Fe~(3+)掺杂后的陶瓷样品均为钙钛矿结构。SEM表明,掺杂Fe~(3+)后陶瓷的晶粒尺寸减小。随着掺杂量的增加,陶瓷样品的体积密度ρv和介电常数ε先增大后减小,介质损耗tanδ先减小后增大。1300℃烧结,x=1.00%的陶瓷样品介电性能最好,ρv=6.03 g/cm3,ε=4560,tanδ=0.004。     

添加TiO_2对0.97Li_(2.3)MgTi_3O_(8.15)-0.03R3725材料的物相组成及介电性能的影响

采用传统固相反应法制备了(1-x)(0.97Li_(2.3)MgTi_3O_(8.15)-0.03R3725)-xTiO_2(0.04≤x≤0.10,质量分数)陶瓷,研究了不同含量TiO_2添加对0.97Li_(2.3)MgTi_3O_(8.15)-0.03R3725 (0.97LMT-0.03R3725)陶瓷烧结特性、相结构、微观形貌以及微波介电性能的影响。结果表明:当x≤8%时,(1-x)(0.97LMT-0.03R3725)-xTiO_2所有组分的物相都能够被Li_2MgTi_3O_8和Li_2O标记,并且随着x的增加,Li_2O特征峰的相对强度在逐渐降低,当x增加到10%时,Li_2O反应完全,TiO_2过量,出现TiO_2的特征峰。随着TiO_2含量的增加,陶瓷的烧结温度、ε_r、τ_f和σ_f(抗弯强度)增加,ρ和Q·f先增加后减小。烧结温度为880℃时,0.92(0.97LMT-0.03R3725)-0.08TiO_2陶瓷表现出了优良的综合性能:ε_r=26.8,Q·f=36386 GHz(7.05 GHz),τ_f=3.02×10~(-6)℃~(-1),σ_f=182.5 PMa。且在此温度下介质材料与Ag电极兼容性良好,表明该材料是制备LTCC器件的备选材料。     

Ce~(3+)掺杂对0.65CaTiO _3–0.35LaAlO_3陶瓷微波介电性能的影响

以EDTA为络合剂,采用聚合物前驱体法合成了0.65CaTiO_3–0.35(La_(1–x)Ce_x)AlO_3(CTLCA–x)微波介质陶瓷。研究了Ce~(3+)取代La~(3+)对陶瓷微波介电性能、显微结构以及晶体结构的影响。结果表明:采用聚合物前驱体法合成的CTLCA–x陶瓷,相比于传统固相法,烧结温度降低了125℃左右,在所研究的组成范围内均能形成正交相固溶体,随着Ce~(3+)掺杂量x的逐渐增加,单位晶胞体积减小,陶瓷的品质因数Q×f和介电常数ε_r均增加,但频率温度系数τ_f下降。当x=0.2时,CTLCA~–0.2陶瓷在1 325℃保温3 h烧结后具有最佳的微波介电性能:ε_r=42.7,Q×f=39 159 GHz,τ_f=–7×10~(–6)/℃。     

Sr和Mn复合掺杂对Ca_(0.3)(Li_(1/2)Sm_(1/2))_(0.7)TiO_3微波介电性能的影响

采用固相法,选择SrCO_3和MnO_2通过A/B位复合掺杂Ca_(0.3)(Li_(1/2)Sm_(1/2))_(0.7)TiO_3体系,制备了(Ca_(15/16)Sr_(1/16))_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)Ti_(1-x)Mn_xO_3微波介质陶瓷,研究了Sr~(2+)含量固定为1/16时,不同Mn~(4+)含量对陶瓷微波介电性能的影响。结果表明,复合掺杂使陶瓷致密化温度由1 300℃逐渐降低至1 200℃,随着Mn掺杂量增加,晶胞体积和晶粒尺寸均略有减小,陶瓷致密度逐渐提高。(Ca_(15/16)Sr_(1/16))_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)Ti_(0.94)Mn_(0.06)O_3陶瓷在1200℃烧结5h具有优良的微波介电性能:相对介电常数ε_r=113,品质因数Q_f=4705 GHz,谐振频率温度系数τ_f=36 ppm/℃。     

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.     

3-溴甲基-3-甲基氧杂环丁烷的合成

以2,2-二溴甲基丙醇（BBMP）为初始原料,通过与碱发生关环反应生成3-溴甲基-3-甲基氧杂环丁烷（BrMMO）。讨论了碱的种类和用量对BBMP关环产率的影响以及反应体系中碱的浓度、反应温度和反应时间对合成BrMMO产率的影响。通过实验确定的最佳工艺条件为：BBMP与NaOH摩尔比为1.0∶1.1,NaOH醇溶液的质量分数为12%,反应温度为78℃,反应时间为4h时,BrMMO产率为65%。最终产品经元素分析、IR和1HNMR检测确定为BrMMO。该试验工艺简单,原料易得,且溶剂便于回收、污染小。     

3-叠氮甲基-3-甲基氧丁环的合成

以三羟甲基乙烷与碳酸二乙酯为原料,经环化反应合成了3-羟甲基-3-甲基氧丁环(HMM O)。在低温下,HMM O与对甲苯磺酰氯反应生成3-磺酸酯甲基-3-甲基氧丁环(M TM O)。M TM O和叠氮化钠发生叠氮化反应形成叠氮单体3-叠氮甲基-3-甲基氧丁环(AMM O)。三步反应收率分别为76%,96%,85%。用核磁、红外、元素分析和DSC表征了化合物的结构与性能。结构鉴定表明为目标化合物AMM O。     

3-溴甲基-3-甲基氧杂环丁烷的合成

以2,2-二溴甲基丙醇(BBMP)为初始原料,通过与碱发生关环反应生成3-溴甲基-3-甲基氧杂环丁烷(BrMMO).讨论了碱的种类和用量对BBMP关环产率的影响以及反应体系中碱的浓度、反应温度和反应时间对合成BrMMO产率的影响.通过实验确定的最佳工艺条件为:BBMP与NaOH摩尔比为1.0∶1.1,NaOH醇溶液的质量分数为12%,反应温度为78℃,反应时间为4 h时,BrMMO产率为65%.最终产品经元素分析、IR和1HNMR检测确定为BrMMO.该试验工艺简单,原料易得,且溶剂便于回收、污染小.     

The Preparation and Crystal Structure of TlMnCl3, TlFeCl3, TlCoCl3 and TlNiCl3

The compounds TlMnCl₃, TlFeCl₃, TlCoCl₃ and TlNiCl₃ were prepared by heating T1C1 with the corresponding transition metal dichloride in an evacuated ampoule. Atomic positions were determined from powder photographs. All four compounds were found to be related to the perovskite type structure. TlMnCl₃ has a cubic structure, space group Pm3m, with a_o = 5.025 Å. The other three compounds are hexagonal, probable space group P6₃mc, with cell dimensions (in Å) a₀ = 6.976 and c₀ = 6.008 for the Fe compound, a₀ = 6.907 and c₀ = 5.981 for the Co compound and a₀ = 6.863 and c₀ = 5.881 for the Ni compound. The three hexagonal compounds are isomorphous. A measureable concentration of basal plane stacking faults was found to occur in TlFeCl₃ and also, to a lesser degree, in TlCoCl_3.     

Tunable color emission in LaScO3:Bi3+,Tb3+,Eu3+ phosphor

LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ (x = 0 − 0.04, y = 0 − 0.05, z = 0 − 0.05) phosphors were prepared via high-temperature solid-state reaction. Phase identification and crystal structures of the LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ phosphors were investigated by X-ray diffraction (XRD). Crystal structure of phosphors was analyzed by Rietveld refinement and transmission electron microscopy (TEM). The luminescent performance of these trichromatic phosphors is investigated by diffuse reflection spectra and photoluminescence. The phenomenon of energy transfer from Bi³⁺ and Tb³⁺ to Eu³⁺ in LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ phosphors was investigated. By changing the ratio of x, y, and z, trichromatic can be obtained in the LaScO₃ host, including red, green, and blue emission with peak centered at 613, 544, and 428 nm, respectively. Therefore, two kinds of white light-emitting phosphors were obtained, LaScO₃:0.02Bi³⁺,0.05Tb³⁺,zEu³⁺ and LaScO₃:0.02Bi³⁺,0.03Eu³⁺,yTb³⁺. The energy transfer was characterized by decay times of the LaScO₃:xBi³⁺, yTb³⁺, zEu³⁺ phosphors. Moreover absolute internal QY and CIE chromatic coordinates are shown. The potential optical thermometry application of LaScO₃:Bi³⁺,Eu³⁺ was based on the temperature sensitivity of the fluorescence intensity ratio (FIR). The maximum S_a and S_r are 0.118 K⁻¹ (at 473.15 K) and 0.795% K⁻¹ (at 448.15 K), respectively. Hence, the LaScO₃:Bi³⁺,Eu³⁺ phosphor is a good material for optical temperature sensing.     

2,2,3-三氯-3-苯基-3-(3-甲基苯甲酰基)丙腈的合成研究

以苯甲酰氯、四氯化碳、间甲基苯甲酰氰为原料,合成了标题化合物。重点考察了氰化过程中不同原料配比、反应温度、时间、溶剂和催化剂用量对收率的影响。实验结果表明,其最佳反应条件为:n(1,1,2-三氯-2-苯基乙烯)∶n(3-甲基苯甲酰氰)=1∶1.2,二氯甲烷为反应溶剂,3 mmol催化剂三乙胺,室温反应5 h,总收率达80.6%。     

Thermal analyses of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Thermal analyses of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB–HV)], and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by T_o = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight-loss rate was at a maximum was T_p = 0.91B + 320, and the temperature at which degradation was completed was T_f = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), T_o = 0.96B + 308, T_p = 0.99B + 320, and T_f = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), T_o = 1.11B + 305, T_p = 1.10B + 319, and T_f = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight-loss step change. The incorporation of 30 mol % 3-hydroxyvalerate (HV) and 15 mol % 3-hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures T_o, T_p, and T_f relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001