植物生长照明用La_(2)Mg_(4/3)Sb_(2/3)O_(6)∶Mn^(4+)红色荧光粉的制备及光谱特性

采用传统高温固相法制备了一系列La_(2)Mg_(4/3)Sb_(2/3-x)O_(6)∶xMn^(4+)红色荧光粉,并对其结构、形貌和光谱特性进行了研究。研究结果表明:La_(2)Mg_(4/3)Sb_(2/3)O_(6)与La_(2)Mg_(4/3)Nb_(2/3)O_(6)具有相同的双钙钛矿结构,Mn^(4+)掺杂对荧光粉的结构没有影响。La_(2)Mg_(4/3)Sb_(2/3-x)O_(6)∶xMn^(4+)荧光粉在360与510 nm处有两个较宽的激发峰,分别对应Mn^(4+)的^(4)A_(2g)→^(2)T_(2g)与^(4)A_(2g)→^(4)T_(2g)跃迁。在360 nm激发下,La_(2)Mg_(4/3)Sb_(2/3-x)O_(6)∶xMn^(4+)荧光粉在710 nm处呈现出较强的红光发射峰,对应Mn^(4+)的^(2)E_(g)→^(4)A_(2g)跃迁发射。Mn^(4+)在La_(2)Mg_(4/3)Sb_(2/3)O_(6)基质中的最佳掺杂浓度为0.004,此时的量子效率高达89.6%,色纯度为99%。根据激发光谱和发射光谱分析了Mn^(4+)在La_(2)Mg_(4/3)Sb_(2/3)O_(6)基质中的晶体场强,并计算了晶体场参数D_(q)、B和C。结合Mn^(4+)的位型坐标图分析了La_(2)Mg_(4/3)Sb_(2/3-x)O_(6)∶xMn^(4+)荧光粉的温度猝灭过程,计算得到其激活能为0.355 eV。最后,对比了La_(2)Mg_(4/3)Sb_(2/3-x)O_(6)∶xMn^(4+)荧光粉的发射光谱与植物光敏色素红外吸收型(P_(R))、远红外吸收型(P_(FR))的吸收光谱,并初步评估了其在LED植物照明领域的应用前景。

碱金属离子共掺Sr_(3)Ga_(2)Ge_(4)O_(14)∶Dy^(3+)发光性能研究

本文采用高温固相法制备了一系列新型Sr_(3-x)Ga_(2)Ge_(4)O_(14)∶xDy^(3+)(x=0~0.40)(摩尔分数)及Sr_(2.68)Ga_(2)Ge_(4)O_(14)∶0.16Dy^(3+),0.16M^(+)(M=Li、Na、K)荧光粉。EDS能谱分析证实该荧光粉中存在Sr、Ga、Ge、O、Dy元素。系列Sr_(3-x)Ga_(2)Ge_(4)O_(14)∶xDy^(3+)在350 nm光激发下产生了以568 nm为主波长,对应于^(4)F_(9/2)→^(6)H_(13/2)跃迁的强黄光发射。荧光粉的发射光谱显示,其发射强度随Dy^(3+)浓度的增加而变化,且当x=0.16时达到最强。共掺杂碱金属M(M=Li、Na、K)作为电荷补偿离子,其中Li^(+)对增加Dy^(3+)的发射强度效果最明显,使得荧光粉的发射强度提高到没有电荷补偿离子时的2倍。此外,随着Dy3+掺杂浓度的提高,荧光粉的荧光寿命不断减少。最后探讨了荧光粉Sr_(2.68)Ga_(2)Ge_(4)O_(14)∶0.16Dy^(3+),0.16Li^(+)的CIE色度坐标和热稳定性,其CIE色度坐标为(0.3719,0.4046),位于黄色区域,在453 K的发光强度约为其室温发光强度的95.5%。因此,Dy^(3+),Li^(+)共掺杂Sr_(3-x)Ga_(2)Ge_(4)O_(14)荧光粉是潜在的显示器件和白光LED器件候选材料。

Cu掺杂对Sr_(3)YCo_(4-x)Cu_(x)O_(10.5+δ)多晶的结构与物理性能的影响

采用固相反应法制备了Sr_(3)YCo_(4-x)Cu_(x)O_(10.5+δ)(x=0~1.0)系列多晶。利用热重-差示扫描量热分析、X射线衍射等表征了多晶的有序化相变,以及Cu掺杂对结构、热电输运性能和磁性能的影响。在固溶范围内(x=0~0.4),观察到XRD的有序峰(103)和(215),说明四方Sr_(3)YCo_(4-x)Cu_(x)O_(10.5+δ)多晶为超结构,这与合成时1000℃以上的吸氧(δ)放热相变有关;当x=0.6~1.0时,978℃在晶界处形成了单斜杂相。当x=0~0.4时,多晶呈半导体输运行为。随着Cu掺杂量的增加,空穴载流子浓度和迁移率增大,电阻率明显下降;此外,Co^(3+)离子自旋态降低,自旋熵增大,载流子浓度和自旋熵的共同作用使x=0~0.2多晶的热电势不变,x=0.4的热电势降低。磁化强度和铁磁转变温度(T_(c))降低,磁结构由G-型反铁磁转变为铁磁。在进行二次烧结后,300 K时电阻率明显降低,热电势为一次烧结的2倍,认为二次烧结提高结晶程度及铁磁有序排列。

Gd掺杂对CaCu_3Ti_4O_(12)陶瓷材料压敏性能的影响

采用固相法制备了Ca_（1-x）Gdx_Cu_3Ti_4O_（12）（x=0～0.09）陶瓷系列样品,利用X射线衍射、Raman光谱和正电子湮没等技术手段,对系列样品的微观结构、缺陷浓度进行测试和表征。结果表明,在整个掺杂范围内体系未发生结构相变,掺杂引起体系晶格膨胀、分子极化率增加;随Gd掺杂量x的增加,空位型缺陷增加。电性能测试结果表明,适量Gd掺杂（x=0.01）有利于改善体系的压敏性能,而过量Gd掺杂（x=0.07～0.09）会阻碍晶界势垒的形成,因而抑制体系的压敏性能。讨论了体系微观结构、空位型缺陷浓度及晶界势垒高度等因素对体系压敏性能的影响特征。

Cu掺杂Ca_(3)Co_(4)O_(9+δ)中温固体氧化物燃料电池阴极材料

采用固相法制备了Ca_(3)Co_(4-x)Cu_(x)O_(9+δ)(x=0,0.1,0.3,0.5)阴极材料,研究了Cu离子掺杂对材料的物相组成、电极微观形貌、电化学性能、热膨胀系数、电导率及单电池输出性能的影响。结果表明:在900℃的煅烧合成温度下,未掺杂与Cu掺杂量为x=0.1的生成产物具有相同单一物相晶体结构(JCPDS 21-0139),Cu掺杂使晶胞参数略有增加。掺杂量为x=0.1的阴极膜层呈现出最疏松多孔状态,有利于氧气在阴极的扩散传输,相应的极化阻抗最小(700℃时极化阻抗为0.85Ω·cm^(2),为未掺杂的42.9%),可以高效地催化氧气在阴极处的还原反应,而且具有最高的电子电导率(相比未掺杂的提高了1.6倍),提升了阴极反应过程中的电荷转移效率。采用Ca_(3)Co_(3.9)Cu_(0.1)O_(9+δ)为阴极的单电池输出性能明显优于其他组分作为阴极时的性能(700℃时功率密度峰值约为79 mW·cm^(-2),为未掺杂的1.9倍)。因此,Cu掺杂的Ca_(3)Co_(4)O_(9+δ)具有作为中温固体氧化物燃料电池阴极材料的应用潜力。

Improvement of Coercive Force of(CoFe)_3O_4 by Doping Ce

Ce_x(CoFe)_(3-x)O_4 ferrites with different contents of Ce have been prepared by wetchemical method. The phases, morphologies and magnetic properties of the products were studied.It has been found that the products were a single phase with spinel structure and consisted of granular particles in most cases.The coercive force of the products increased with the increase of concentration of Ce￣(4+) in the reaction solution.On the other hand,if Ce￣(3+) and Ce(OH)_4 were present in the reaction solution,some rod-shape crystals in the products were observed, which causes a great increase in coercive force,and the optimum value was obtained when[Ce￣(3+)] was about 5% of the total([Ce￣(3+)]+[Ce￣(4+)]).

Gd^(3+)掺杂铁氧体吸波材料的制备及性能研究

运用电磁吸波材料是解决电磁辐射/干扰难题和提升武器装备隐身性能的有效手段。基于掺杂诱导作用调控电磁特性的策略,以稀土离子钆(Gd^(3+))为掺杂离子,采用溶剂热法制备Gd^(3+)掺杂铁氧体(GdxFe3-xO4)磁性吸波材料,并探究Gd^(3+)掺入量对材料微观结构、磁性能和吸波性能的影响。结果表明:Gd^(3+)的掺入对产物晶型和微观形貌影响不显著,磁性颗粒尺寸随着Gd^(3+)掺入量的增加而减小。适量Gd^(3+)的掺入可以提高材料的磁性能,Gd0.04Fe2.96O4的饱和磁化强度达66.49emu/g。此外,当在基体填充率为70%时,最大反射损耗为-47.25dB,有效吸收带宽为5.94GHz,这表明GdxFe3-xO4磁性材料有望成为一种极具应用价值的电磁吸波材料。

Jahn-Teller distortion assisted interstitial nitrogen engineering:Enhanced oxygen dehydrogenation activity of N-doped Mn_(x)Co_(3-x)O_(4) hierarchical micro-nano particles

Rational design of earth-abundant transition metal oxides catalysts is highly desirable for developing sustainable chemical processes.Herein,we demonstrate a prospective interstitial nitrogen engineering for fabricating oxygen vacancies(OVs)-rich nitrogen-doped-Mn_(x)Co_(3-x)O_(4)(N-Mn_(x)Co_(3-x)O_(4))oxide catalyst,in which the ratio of OVs concentration of N-Mn_(x)Co_(3-x)O_(4)to Mn species is as high as 1:1,according to the characterizations of X-ray absorption(XAS)and X-ray photoelectron(XPS)spectroscopies.The promising strategy of interstitial nitrogen engineering through lattice distortion caused by the Jahn-Teller effect can significantly increase the amount of interstitial nitrogen.The resulting catalyst enables an additive-free aerobic dehydrogenation coupling of aromatic amine to afford azo compounds with>99%yield and>99%selectivity at 60☆.We observed the superb catalytic activity is promoted by the enhanced oxygen mobility in OVs,which were created by the interstitial nitrogen in the catalyst matrix.The presence of interstitial nitrogen in transition metal oxides in this study shows how the manipulation of catalyst matrix can increase the OV sites to promote aerobic oxidation reaction.

Honeycomb-like g-C_(3)N_(4)/CeO_(2)-x nanosheets obtained via one step hydrothermal-roasting for efficient and stable Cr(Ⅵ) photo-reduction

Graphitic carbon nitride(g-C_(3)N_(4))-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy.In this work,we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C_(3)N_(4)/CeO_(2) nanosheets with abundant oxygen vacancies(g-C_(3)N_(4)/CeO_(2)-x).The hydrothermal-roasting and incomplete-sealed state can(i)generate an in-situ reducing atmosphere(CO,N2,NH3) to tune the concentration of oxygen vacancies in CeO_(2);(ii) beneficial to prevent continuous growth of g-C_(3)N_(4) and results in honeycomb-like g-C_(3)N_(4)/CeO_(2)-x hybrid nanosheets.What is more,the g-C_(3)N_(4)/CeO_(2)-x photocatalyst exhibited extended photoresponse range,increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs.As a proof-of-concept application,the optimized g-C_(3)N_(4)/CeO_(2)-xnanosheets could achieve 98% removal efficiency for Cr(Ⅵ) under visible light irradiation(λ≥420 nm)within 2.5 h,which is significantly better than those of pure g-C_(3)N_(4) and CeO_(2).This work provides a new idea for more rationally designing and constructing g-C_(3)N_(4)-based catalysts for efficient extended photochemical application.

Structural,microstructural and dielectric properties of Ba_(1-x)La_(x)Tie_(1-x/4)O_(3)prepared by sol gel method

Detailed structural and dielectric properties of Lanthanum-doped barium titanate Ba_(1-x)La_(x)Tie_(1-x/4)O_(3)ceramic powders BLTx(where x=0:00;0.10;0.20;0.30 and 0.40)/BT,BLT10,BLT20,BLT30 and BLT40,synthesized by the sol gel process,calcined at 900℃for 3 h and sintered at 1250○C for 6 h,have been investigated.The phase formation and crystal structure of the samples were checked by X-ray diffraction(XRD)and Raman spectroscopy.The samples crystallize in the pure perovskite structure that transforms from tetragonal to pseudocubic under doping with La;results that have been confirmed by Rietveld Refinement technique.The estimated average crystallite size of the samples was about 23 nm.Dielectric parameters(dielectric permittivity and losses)were determined in the temperature range room temperature(RT)-280℃and in the frequency range 500 Hz-2 MHz.La doping gives rise to a strong decrease of the ferro-to-paraelectric transition temperature,and the frequency dependence of the permittivity shows that the samples with x=0.00 and x=0.10 reach their resonance frequency.The frequency dependence of impedance and electric modulus properties were studied over a wide frequency range from 1 kHz to 2MHz at various temperatures to confirm the contributions from grains and grain-boundaries.The complex impedance analysis data have been presented in the Nyquist plot which is used to identify the corresponding equivalent circuit and fundamental circuit parameters;it was found that the grain boundaries resistance is dominant at room temperature.The frequency dependence of the parameters permittivity,losses and AC conductivity reveals that the relaxation process is of the Maxwell-Wagner type of interfacial polarization.

Preparation of the Solid Electrolytes Li_(4+x)Al_xSi_(1-x)O_4-yAl_2O_3 by the Sol-Gel Method and Study of Their Ionic Conductivity

The Li_(4+x)Al_xSi_(1-x)O_(4-y)Al_2O_3 (x = 0 to 0.5, y = 0 to 0.5) ionconductors were prepared by the Sol-Gel method and examined in detail. The powder and sinteredsamples were characterized by TG-DTA, XRD, SEM, and AC impedance techniques. The experimentalresults show that the conductivity and sinterability increase with the amount of excess Al_2O_3 inthe silicate. The particle size of the powder samples is about 0.13 μm. The maximum conductivity at18 ℃ is 3.057 * 10^(-5) s/cm for Li_(4.4)Al_(0.4)Si_(0.6)O_4-0.3 Al_2O_3.

陶瓷-聚合物复合固态电解质膜的制备与性能研究

NASICON型快离子导体Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)具有较高的离子电导率、较宽的电化学窗口及良好的水和空气稳定性,但其界面接触性能差。石榴石型Li_(7)La_(3)Zr_(2)O_(12)(LLZO)锂离子电导率高、电化学窗口较宽且热稳定性好,但其立方相结构不稳定,影响其实际应用。采用溶液浇筑法,制备纯PVDF-LiTFSI电解质膜和以PVDF为基、3种不同质量比的Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)的固态电解质膜,并探讨纯PVDF-LiTFSI电解质膜和3种不同质量比的活性无机电解质填料对复合固态电解质离子电导率的影响。结果表明,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时,电解质膜的XRD图谱的衍射峰比纯PVDF-LiTFSI下降更为明显,电化学窗口为3.9 V左右,表现出更好的稳定性。在不同温度下分别测量其离子电导率发现,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时的电解质膜均高于纯PVDF-LiTFSI电解质膜和Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为2∶1和3∶1时的电解质膜。将其装配成电池后发现,0.1C下电池首次充放电比容量分别为90 m A·h/g和87 m A·h/g。以0.5C的电流循环25圈,放电比容量从57 mA·h/g衰减至51mA·h/g,容量保持率为99.7%。所以,以PVDF为基、Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1的固态电解质膜有优良的倍率性能和循环稳定性能。

铁离子掺杂对铜铬黑颜料呈色性能的影响

为改善CuCr_(2)O_(4)黑色颜料呈色性能,将Fe^(3+)掺杂进入CuCr_(2)O_(4)晶体中,采用共沉淀法制备CuCr_(2-x)Fe_(x)O_(4)(x=0,0.04,0.05,0.06,0.07),并对所制备样品进行TG-DTA、XRD、SEM、Raman、XPS、UV-Vis吸收光谱和色度值的测试与表征。结果表明,Fe以三价态固溶进入Cr3+位置,未出现杂质相,得到的CuCr_(2-x)Fe_(x)O_(4)晶粒细小、分散均匀。Fe^(3+)掺杂可减小CuCr_(2)O_(4)的禁带宽度,从1.25 eV减小到1.08 eV,禁带宽度的减小是由于2p(O^(2-))→3d(Fe^(3+))和Fe^(3+)的d-d(^(6)A_(1g)→^(4)T_(1g)和^(6)A_(1g)→^(4)T_(2g))电荷跃迁引起的。禁带宽度的减小使得黑色颜料对可见光(380~780 nm)的吸收率提高,L^(*)值减小,呈现出良好的黑度。得到的最佳黑色颜料为CuCr_(1.95)Fe_(0.05)O_(4),L^(*)=17.63,a^(*)=-0.77,b^(*)=-1.61。

大气等离子喷涂制备SOFC连接体Cu/Mn/Co金属防护涂层

为了进一步提高固体氧化物燃料电池(SOFC)连接体防护涂层的电导率,采用大气等离子喷涂技术(APS)制备了Cu/Mn/Co金属涂层.研究了不同喷涂工艺参数对涂层性能的影响,以及涂层在800℃下的氧化行为.通过XRD,SEM及EDS表征涂层高温氧化过程中的相结构、表面形貌和微观结构演变,采用直流四电极法测量涂层的高温电导率.结果表明,800℃下氧化使金属涂层转变成了MnCo_(2)O_(4)/Cu_(x)Mn_(3-x)O_(4)相.氧化初期,涂层表面和底部出现富Cu层;随氧化时间增加,富Cu层逐渐消失,Cu元素均匀分布在涂层中;当氧化120 h时,涂层表层的CuO层已不连续,与涂层分层且产生微裂纹.同时发现,长时间氧化后涂层截面明显致密化,形成了顶部致密、底部多孔的结构.此外,电流为550 A的涂层试样(No.2)尖晶石相最多,涂层致密度最高,其电导率也最高.800℃下氧化120h后,电流为500,550和600 A的三种涂层试样(No.1~No.3)电导率分别为59.68S,93.55和85.72 S/cm,并且氧化过程中电导率保持稳定.所制备的金属涂层和尖晶石涂层均表现出较好的阻Cr扩散效果,Cr主要以Cr_(2)O_(3)的形式富集在基体和涂层的结合处.