Determination of the supersaturation in the LiIO3–HIO3–H2O system using a refractive index value at near saturation concentration

The exact determination of supersaturation is essential for the studies of crystal growth processes in solutions. Due to peculiarities in the solubility of LiIO₃, the refractive index of the solution is chosen as a measure of the supersaturation instead of undercooling. The experimental setup is based on a refractometer and a special setup to create supersaturation in the cuvette by means of successive evaporation of small amounts of solvent. The refractive index is measured at different solution concentrations and pH and the data are correlated as dependences of concentration and pH on the refractive index. The accuracy of the method and the adequacy of the model are discussed.     

0.2wt% Bi2O3、CuO、B2O3对5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3微波介质陶瓷的性能影响

采用传统的固相反应法,研究了三种烧结助剂Bi2O3、CuO、B2O3对5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3微波介质陶瓷的烧结性能和介电性能的影响。实验结果表明,掺入0.2wt%的Bi2O3、CuO、B2O3产生了液相,有效地降低了体系的烧结温度。Bi2O3和CuO的加入没有改变烧结体的微观形貌,它们介电常数和品质因数随烧结温度的变化趋势和体积密度趋于一致,均在体积密度最大时最高。当温度大于1300℃时,加入0.2wt%B2O3试样有柱状晶体生成,并随着烧结温度的升高而增多,柱状晶体的存在可能促使Q×f值较大的提高,当烧结温度过高时(1350℃),由于柱状晶体过多使得烧结体不均匀导致Q×f值下降。Bi2O3、CuO、B2O3的加入没有改变烧结体的晶相组成,因此所有烧结体均有近零的温度系数。结果表明,加入0.2wt%B2O3的5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3在1325℃烧结温度具有最佳的介电性能:εr=54.87,Q×f=55 726 GHz,τf=-0.6 ppm/℃。     

Sol–gel preparation and photoluminescence properties of Ce-activated Y3Al5O12 nano-sized powders

Trivalent cerium-doped yttrium aluminum garnet (YAG:Ce³⁺) nanoparticles were successfully prepared by a facile sol–gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the as-prepared phosphors. Well-crystallized fine nanoparticles were obtained at 1000 °C. Single-crystal nanoparticles with irregular shapes were obtained, with crystallite sizes ranging between 20 and 60 nm. PL intensity of the particles increased monotonically with decreasing Ce doping concentration and showed the maximum value at 0.1 at%.     

K0.5Na0.5NbO3掺杂对0.94Bi0.5Na0.5TiO3-0.06BaTiO3陶瓷储能性能的影响

采用传统固相反应法制备了K_0.5Na_0.5NbO₃(KNN)掺杂的无铅介电储能陶瓷BNT-BT-KNN,其组分配比为0.94Bi_0.5Na_0.5TiO₃-(0.06-x)BaTiO₃-xK_0.5Na_0.5NbO₃(BNT-BT+xKNN,x=0.00～0.04),并研究了KNN掺杂对BNT-BT基陶瓷材料晶相、微观结构、介电、铁电性能及储能的影响。结果表明：在1 150℃温度下烧成后的陶瓷样品具有纯的钙钛矿结构,且样品的晶粒均匀致密;介电温谱显示,添加KNN后的BNT-BT铁电陶瓷在T_m处的介电峰进一步宽化,表现出更好的温度稳定性和弛豫性;同时随着KNN掺杂量的增加,样品的电滞曲线(P-E曲线)逐渐由“宽胖型”向“细长型”转变,样品的剩余极化强度(P_r)逐渐降低,从而进一步提高了BNT-BT陶瓷的储能性能。在2 kV/mm的场...     

Controlling metal–insulator transition in the hetero-epitaxial VO2/TiO2 bilayer grown on Al2O3

Hetero-epitaxial VO₂/TiO₂ bilayers were synthesized on Al₂O₃ substrates by using pulsed laser deposition, and their physical properties with the changes of oxygen pressure and the substrate orientation were investigated. A metal–insulator transition of the VO₂ was observed only in a narrow oxygen pressure range of 5–20 mTorr. As the oxygen pressure increased, X-ray diffraction peak for the (2 0 0)VO₂ shifted to a lower 2θ position, while the metal–insulator transition temperature (T_MI) decreased by ∼7 K. On the other hand, T_MI was largely varied with substrate orientation. The (2 0 0)VO₂/TiO₂ on the c-plane sapphire showed the highest T_MI of about 350 K, while the (0 0 2)VO₂/TiO₂ on the m-plane sapphire displayed the lowest T_MI of about 310 K. The (1 0 1)VO₂/TiO₂ on the r-plane and the a-plane exhibited T_MI∼340 and 330 K, respectively. The observed variations of T_MI with the oxygen pressure and substrate orientation were presumably due to the change in oxygen content of the VO₂ layer and/or in lattice strain.     

Glass formation and structure of glasses in B2O3―Bi2O3―MoO3 system

The purpose of this paper is to study the glass formation tendency in the ternary system B₂O₃―Bi₂O₃―MoO₃ and to define the main structural units building the amorphous network. A wide glass formation area was determined which is situated near the Bi₂O₃―B₂O₃ side. A liquid phase separation region was observed near the MoO₃―B₂O₃ side for compositions containing below 25 mol% Bi₂O₃ and their microheterogeneous structure was observed by SEM. The phase formation was characterized by X-ray diffraction (XRD). By DTA was established the glass transition temperature (T_g) in the range of 380-420 °C and crystallization temperature (T_x) vary between 420 and 540 °C. The main building units forming the amorphous network are BO₃ (1270 and 1200 cm^− 1), BO₄ (930-880, 1050-1040 cm^− 1), MoO₄ (840-760 cm^− 1) and BiO₆ (470 cm^− 1). It was proved that Bi₂O₃ favors the BO₃ → BO₄ transformations while MoO₃ preserves BO₃ units in the amorphous network.     

Ba(Co1/3Nb2/3)O3微波介质陶瓷预烧温度研究

采用传统固相法制备Ba(Co1/3Nb2/3)O3微波介质陶瓷。研究了预烧温度对其物相组成、显微结构、烧结性能、微波介电性能的影响。结果表明:在不同预烧温度下制备的陶瓷样品主晶相为复合钙钛矿结构的Ba3CoNb2O9,900℃、1000℃有微量Ba3Nb5O15生成。最佳预烧温度为1100℃,在1380℃烧结4 h时,εr=31.8,Q×f=60164GHz,τf=-15×10-6/℃。合适的预烧温度能有效抑制第二相的生成,提升材料致密度,促使主晶相B位有序排列,进而降低介电损耗。     

Bi4Si3O12-Bi4Ge3O12赝二元系统析晶行为及其晶体生长

本文采用固相合成方法制备了Bi4(GexSi1-x)3O12(BGSO)固溶体(x=0～0.4),研究了它的固溶特性和析晶行为。实验结果表明,不同组成混合料在900℃左右固相反应能生成BGSO纯相;XRD分析显示,在x=0～0.4区间内,Bi4Si3O12和Bi4Ge3O12可以完全互溶,其晶格常数随x的增加呈线性增长。采用坩埚下降法生长了x=0.15组成的BGSO混晶,获得了透明晶体,并测试了晶体的光学性能。     

锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2电极过程动力学研究

采用共沉淀法制备锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2,通过循环伏安法和电化学交流阻抗分析,探讨了锂离子在LiNi1/3Co1/3Mn1/3O2中嵌入和脱出的机制。循环伏安测试结果表明,LiNi1/3Co1/3Mn1/3O2材料结构中不存在John-teller效应,从而抑制了电极材料和电解液之间的副反应。电化学交流阻抗测试结果表明,随着电压的升高Rct(电荷转移电阻)值逐渐减小,而随着循环次数的增加Rct值逐渐增大。     

Al2O3掺杂对Ca0.2Sr0.05Li0.375Sm0.375TiO3微波介电性能的影响

采用固相烧结法制备了掺杂Al2O3的Ca0.2Sr0.05Li0.375Sm0.375Ti O3微波介质陶瓷。研究了Al2O3掺杂对Ca0.2Sr0.05Li0.375Sm0.375Ti O3的助烧效果、物相结构、显微组织和微波介电性能的影响规律。结果表明:Al2O3的添加降低了Ca0.2Sr0.05Li0.375Sm0.375Ti O3陶瓷的烧成温度,但对物相基本无影响。此外,高含量Al2O3的添加能促进晶粒细化。此体系陶瓷的最佳介电性能为:Al2O3含量为0.9wt%且烧成温度为1250℃时,εr=110.8、Q·f=4159.6 GHzτf=49.4 ppm/℃。     

Study of amorphous Ge–SiO2–P+Si tunnel junctions

A new method to determine ac conductivity of amorphous Ge using Al-amorphous Ge–SiO₂–P⁺Si tunnel junctions is presented. Frequency dependence of ac conductivity is found to satisfy the power law in the frequency range between 1 and 50 kHz and the density of localized states at the Fermi level is estimated to be ～ 1.7 × 10²⁰ cm^?3 eV^?1 which decreases to ～ 4.5 × 10¹⁹ cm^?3 eV^?1 after annealing at 175°C.Temperature dependence of tunneling conductance of Al-amorphous Ge–SiO₂–P⁺Si junctions is appreciable only near zero bias. Zero bias conductance of the junctions obeys the $\text{T}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}$ law of Mott; the density of localized states obtained from the $\text{T}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}$ law is one order of magnitude smaller than that obtained by ac conductivity measurements, being insensitive to annealing. This behavior of the tunnel junctions differes in many respects from those of Al–Al₂O₃-amorphous Ge tunnel juntions.     

Fe2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Fe2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(简称BCZT)无铅压电陶瓷。借助XRD、SEM、阻抗分析仪等对该陶瓷的相组成、显微结构以及压电和介电性能进行了研究。结果表明,Fe2O3掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度Tc从85℃提高到95℃;当Fe2O3掺杂为0.02wt%～0.1wt%时,陶瓷样品均为ABO3型钙钛矿结构;少量Fe2O3掺杂促进了陶瓷晶粒的生长,但随着Fe2O3掺杂量进一步增加,陶瓷晶粒随之细化;当Fe2O3掺杂量为0.04wt%时,陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因数Qm、介电损耗tanδ和介电常数εr分别为400 pC/N,0.40,51,0.023和3482。     

Tb3+-Eu3+共掺杂2ZnO·2.2B2O3·3H2O的制备和发光性能

采用水热法合成了Tb3+和Eu3+共掺的2ZnO.2.2B2O3.3H2O红色荧光粉。通过固定Eu3+的掺杂浓度为3%(物质的量比:Eu∶Zn=3%),改变Tb3+的掺杂浓度(2%～15%),研究Tb3+掺杂浓度对红色荧光粉晶相结构和光学性能的影响。用X射线衍射和荧光光谱仪对样品的结构和发光性能进行表征,结果表明:随着Tb3+掺杂浓度的升高,样品由晶态向无定形的玻璃态转变;Eu3+的发光强度也逐渐增强;Tb3+与Eu3+之间存在能量传递的过程,且当采用不同的激发波长(220 nm和393 nm)激发时,其能量传递的过程也不一样。     

KLi(HC3N3O3)·2H2O晶体的电光效应和生长研究

本文采用电光系数的粉末测试方法,探索发现了新型电光晶体KLi(HC₃N₃O₃)·2H₂O。根据粉末样品的红外反射光谱和拉曼光谱,计算获得晶格振动对电光系数的贡献值,再加上粉末倍频效应推算的有效非线性光学系数,最终计算出KLi(HC₃N₃O₃)·2H₂O的电光系数为2.37 pm/V,与商用电光晶体β-BBO相当。采用水溶液法进行晶体生长,测试不同原料生长晶体时的过热和过冷曲线,优化生长工艺,获得35 mm×25 mm×10 mm透明晶体。采用X射线定向技术辅以压电系数测量,确定了晶体形貌与各向异性生长速率的对应关系。     

3LiMnPO4·Li3V2（PO4）3正极材料的制备及其电化学性能研究

以五氧化二钒干凝胶、碳酸锰、磷酸二氢铵、碳酸锂、乙炔黑为原料,采用固相法在相对较低的温度条件下合成了x Li Mn PO4·y Li3V2(PO4)3锂离子电池复合正极材料。采用X射线衍射(XRD)、扫描电镜(SEM)对其晶体结构和表面形貌进行表征。结果表明,750℃下烧结15 h合成的3Li Mn PO4·Li3V2(PO4)3为结晶良好的两相结构,颗粒粒径较小且分布比较均匀,其在室温、0.2 C倍率下首次充放电容量分别为144.8 m Ah/g和139.8 m Ah/g,循环50次后容量为130.5 m Ah/g。     

K3ScF6∶Tm3+,Yb3+/CdS光催化复合材料的制备及其光催化性能研究

上转换材料与光催化剂复合可以产生吸收光谱“红移”的效果,对提高光催化剂的降解效率具有重要意义。为了提高CdS对近红外光的利用率,通过高温固相反应法合成了冰晶石结构上转换发光材料K₃ScF₆∶Tm³⁺,Yb³⁺,并采用高能球磨法将其与CdS复合制备出一种新型光催化复合材料K₃ScF₆∶Tm³⁺,Yb³⁺/CdS。采用X射线粉末衍射(XRD)、场发射扫描电镜(SEM)、荧光光谱(PL)和紫外-可见漫反射吸收光谱对其成分、结构和性能进行了系统表征。同时,对不同复合比例下制备的复合催化剂对罗丹明B(RhB)的光降解效率和K₃ScF₆∶Tm³⁺,Yb³⁺/CdS光催化复合材料的光催化机理进行了研究。结果表明,K₃ScF₆∶Tm³⁺,Yb³⁺和CdS的...     

<001>-取向（1-x）PbMg1/3Nb2/3O3-xPbTiO3单晶电卡效应的组分依赖性

以<001>取向的PMN-0.14PT,PMN-0.17PT,PMN-0.28PT为代表,研究了PT含量对PMN-x PT单晶电卡效应的影响。通过测试单晶的变温电滞回线,计算了PMN-0.14PT,PMN-0.17PT,PMN-0.28PT的电卡效应。计算结果显示PMN-0.14PT,PMN-0.17PT,PMN-0.28PT单晶的电卡效应最大值随着PT含量的增加而增加,在较小的4 k V/mm电场情况下,分别达到1 K,1.17 K,1.96 K。此外,电卡效应峰发生在居里温度介电峰附近,随着PT含量的增加,电卡效应峰越来越尖锐并移向高温方向。     

Synthesis and Structural Characterization of Two New Layered Inorganic–Organic Hybrid Zinc Phosphites Templated by Cyclam: Zn(HPO3)2·0.5(C10H28N4) and Zn2(HPO3)3·0.5(C10H28N4)

Abstract  

Using 1,4,8,11-tetraazacyclotetradecane (cyclam) as a template, two new layered zincophosphites, Zn(HPO₃)₂·0.5(C₁₀H₂₈N₄) (1) and Zn₂(HPO₃)₃·0.5(C₁₀H₂₈N₄) (2), were synthesized and characterized by single crystal X-ray diffraction. The two new compounds crystallize in the triclinic system with the space group P − 1 and the cell parameters: a = 8.3130 ?, b = 8.7289 ?, c = 9.0055 ?, α = 106.90(1), β = 95.56(1), γ = 105.30(1), V = 592.31 ?³, Z = 2 for 1 and a = 9.0406 ?, b = 9.4234 ?, c = 9.4519 ?, α = 91.19(1), β = 100.73(1), γ = 106.85(1), V = 754.82 ?³, Z = 2 for 2. Both structures are described in terms of phosphometallic slabs hosting the cyclam cation.     

Infrared transmission of (R2O OR R’O)–(TiO2, Nb2O5 OR Ta2O5)-Al2O3 glasses

The new families of aluminate glasses obtained by the present authors from their melts in the systems K₂O–Ta₂O₅–Al₂O₃, Na₂O–K₂O–Ta₂O₅–Al₂O₃, K₂O –Cs₂O– Ta₂O₅–Al₂O₃, K₂O–Nb₂O₅–Al₂O₃, Na₂Oz.sbnd;K₂O–TiO₂–Al₂O₃, BaO–TiO₂–Al₂O₃, BaO–ZrO₂–TiO₂–Al₂O₃ and Na₂O–K₂O–BaO–ZrO₂–Ta₂O₅–TiO₂ –Al₂O₃ showed high transmissions of visible and infrared (IR) radiation ranging from 0.4 to about 6 μm, as well as high refractive indices up to 2.0. Their physical and chemical properties such as glass-forming ability, softening temperature, hardness and hygroscopicity were comparable to conventional silicate glasses. These properties are useful for IR applications. The cause of the high IR transmission of the aluminate glasses was interpreted in terms of the masses of the constituent cations and the single bond strengths of the cations with oxygen ions.     

Glass formation and structure of glasses in the ZnO―Bi2O3―WO3―MoO3 system

The glass formation region in the ternary ZnO―Bi₂O₃―WO₃ system is determined by melt quenching technique (cooling rates 10¹-10² K/s). New original glasses are obtained in a narrow concentration range with high WO₃ content (60-75 mol%). Homogeneous glasses of the composition (100 − x)[0.2ZnO·0.3Bi₂O₃·0.5WO₃]xMoO₃, were obtained between 20 and 60 mol% MoO₃. Characterization of the amorphous samples was made by x-ray diffraction (XRD), differential thermal analysis (DTA) and infrared spectroscopy (IR). The thermal stability of glasses decreases with the increasing of MoO₃ content. The glass transition temperature, T_g, varies between 340-480 °C, while the crystallization temperature, T_x, varies between 388-531 °C. The tungstate glasses possess higher crystallization temperature (T_x over 500 °C) in comparison with the other vanadate and molybdate non-traditional glasses. The glass network is realized by transformation of three-dimensional structure of WO₃ into a layered one, consisting mainly of WO₆ units. We supposed that the network of quaternary glasses is built up by MoO₄, MoO₆ and WO₆. At low concentration ZnO and Bi₂O₃ facilitate the disorder in the supercooled melts, while at high concentration stimulate crystallization processes. These oxides belong to the intermediate ones.