固体氧化物燃料电池Sr_(2)Fe_(1+x)Mo_(1-x)O_(6-δ)双钙钛矿阳极的改性研究进展

固体氧化物燃料电池(SOFC)是下一代能源系统的重要组成部分,拥有比传统发电方式更高的能量转换效率、燃料选择范围广、无需贵金属催化剂,环境友好。阳极作为SOFC中燃料氧化的电化学反应场所,其材料选择对电池性能的影响较大。截至目前,阳极材料的研究已经从最开始的金属基陶瓷材料发展到氧化物型材料。其中双钙钛矿作为钙钛矿材料的衍生物更是成为了目前的主流选择。Sr_(2)Fe_(1+x)Mo_(1-x)O_(6-δ)(SFMO)因为优异的电导率、抗积碳和耐硫性得到广泛关注,但将其用于商业化还有一些问题亟待解决,为进一步提升SFMO阳极的催化活性和稳定性,研究人员将目光放在了材料的改性上。概述了通过不同改性方法来提升SFMO阳极性能的研究进展,分别从掺杂(A,B掺杂和A/B共掺),A位缺位和表面修饰三个方面进行阐述,从物相、结构和电化学性能方面对阳极进行比较,分析了各改性方法对电化学性能,长期稳定性和氢裂解、氧化反应能力的影响。

Pr^(3+)掺杂Sr_(2)LaTaO_(6)红色荧光粉的合成和发光性能分析

为寻找能应用于白光LED的红色荧光粉,以稀土氧化物为原料,采用高温固相法制备Pr^(3+)掺杂Sr_(2)LaTaO_(6)系列红色荧光粉,再通过XRD、SEM及荧光光谱仪等仪器对样品的物相结构、形貌特征、荧光特性、衰减寿命和荧光热猝灭等性能进行实验分析。结果表明:样品物相纯正、结晶度好,Pr^(3+)的掺杂没有改变基质的晶体结构;样品可以被蓝光有效激发,发出色坐标为(0.6630,0.3366)的红光;Pr^(3+)的最佳掺杂浓度(摩尔分数)为0.1%,随着Pr^(3+)掺杂浓度(摩尔分数)不断高于该浓度,其荧光强度和衰减寿命都会递减;样品在室温到400 K这一温度范围内热稳定性良好。表明Pr^(3+)掺杂的Sr_(2)LaTaO_(6)红色荧光粉有望应用于白光LED。

SOFC复合阳极材料Sr_2Mg_(0.3)Co_(0.7)MoO_6/GDC的制备及性能研究

采用柠檬酸燃烧法合成了Sr_2Mg_(0.3)Co_(0.7)MoO_6(SMCO)阳极粉体和Ce_(0.8)Gd_(0.2)O_3(GDC)电解质粉体。制备了不同比例的SMCO-GDC复合阳极,利用X射线衍射仪、扫描电镜和交流阻抗谱研究了GDC含量对复合阳极的物相结构、显微形貌和电性能的影响。研究结果表明,SMCO和GDC在1250℃下具有良好的化学相容性,少量GDC的加入可以提高复合阳极的电化学性能。当SMCO与GDC质量比为4:1时,对称电池极化电阻最小,电池的功率密度最大。GDC含量的增加,不利于电池性能的提高。

掺杂对Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)阳极材料电化学性能影响研究进展

固体氧化物燃料电池是一种将化学能直接转化为电能的清洁、高效的能量转化器件。传统的金属陶瓷阳极材料存在碳沉积、硫中毒和氧化还原循环稳定性差等缺点,限制了其商业化应用。为了改善金属陶瓷阳极在实际应用中遇到的问题,近年来混合电子-离子导体的钙钛矿陶瓷阳极得到了长足的发展。其中,结构组成为Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)的阳极材料具有较好的稳定性、较高的电导率、合适的热膨胀系数和优异的电化学性能,因而被广泛研究,特别是元素掺杂。本工作根据钙钛矿ABO_(3)可掺杂的位置,分别从A位、B位和O位掺杂进行讨论,总结了各元素掺杂和掺杂量对Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)的容忍因子、晶体结构、稳定性、电导率、热膨胀系数和电化学性能等的影响。这些掺杂策略为改性Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)钙钛矿阳极提供了新颖的思路,此思路也可用于改性其他同类钙钛矿阳极材料。最后总结了Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)和典型钙钛矿陶瓷阳极材料的发展方向:一方面可通过阴离子掺杂和共掺杂策略进一步提高钙钛矿陶瓷阳极材料的性能;另一方面可采用密度泛函理论进一步阐明元素掺杂的作用机制。

固体氧化物电池Sr_(2-x)Fe_(1.5)Mo_(0.5)O_(6-δ)氧电极材料的电化学性能

本文系统研究了Sr缺位对Sr_(2-x)Fe_(1.5)Mo_(0.5)O_(6-δ)氧电极材料晶体结构、电导率和电化学性能的影响规律。结果表明Sr缺位导致晶胞体积增大,降低了氧溢出的温度,增强了材料内部晶格氧的活性,Sr_(1.95)Fe_(1.5)Mo_(0.5)O_(6-δ)材料具有最大的电导率为38.4 S/cm。Sr缺位提高了材料的氧还原反应活性,800℃时Sr_(2-x)Fe_(1.5)Mo_(0.5)O_(6-δ)、Sr_(1.95)Fe_(1.5)Mo_(0.5)O_(6-δ)、Sr_(1.9)Fe_(1.5)Mo_(0.5)O_(6-δ)对称电池在空气下的极化电阻分别为0.102、0.070和0.096Ω·cm^(2)。燃料电池模式下,阳极支撑的NiO-YSZ(SL)/NiO-YSZ(FL)/YSZ/SDC/Sr_(1.95)Fe_(1.5)Mo_(0.5)O_(6-δ)单电池在850、800、750和700℃下的峰值功率密度分别达到1459、953、682和420 mW/cm^(2)。电解池模式下单电池在20%H_(2)O-H_(2)、800℃和1.5 V电压下的电流密度达到-1300 mA/cm^(2)。同时电解池在800℃和-500 mA/cm^(2)条件下稳定运行了100 h,单电池的衰减速率约为0.001 V/h,表现出良好的运行稳定性。

Sm^(3+)掺杂Sr_(2)YSbO_(6)红色荧光粉的制备及发光性能研究

采用高温固相法合成新型Sr_(2)YSbO_(6)∶Sm^(3+)红色荧光粉。使用X射线衍射仪(XRD)、荧光粉激发光谱与热猝灭分析系统、稳态-瞬态光谱仪等手段对样品的物相结构、光致发光光谱、荧光淬灭等性能进行分析。结果表明:合成的样品不含杂质相,在405nm光激发下可以发射出色坐标为(0.598,0.399)的红光;Sm^(3+)最佳掺杂浓度为2.0%;Sm^(3+)之间的交换相互作用是导致Sr_(2)YSbO_(6)∶Sm^(3+)样品荧光浓度猝灭发生的原因;Sr_(2)Y_(0.980)SbO_(6)∶0.020Sm^(3+)样品的荧光寿命为1.37ms,在293~480K之间具有比较好的热稳定性。因此,Sr_(2)YSbO_(6)∶Sm^(3+)红色荧光粉有望作为白光LED用红色荧光粉。

基于能量传递可调光色荧光粉Ca_(2)LaTaO_(6)∶Dy^(3+),Sm^(3+)的发光性质及其发光二极管器件应用

通过固相反应法设计了Dy^(3+),Sm^(3+)共掺杂双钙钛矿结构Ca_(2)LaTaO_(6)(CLTO)光色可调的白光发光二极管(LED)荧光粉.通过Rietveld精修计算,确定了Ca_(2)LaTaO_(6)的晶体结构参数和Dy^(3+),Sm^(3+)离子的晶格占位,并用密度泛函理论(DFT)计算了禁带宽度.激发/发射光谱和荧光衰减行为证实了共掺杂体系中Dy^(3+)到Sm^(3+)的能量传递.Dy^(3+)→Sm^(3+)的能量传递机制为电偶极-电偶极相互作用,离子间的临界距离为1.176 nm.基于Dy^(3+)→Sm^(3+)的能量传递,可通过调节Dy^(3+)/Sm^(3+)离子的掺杂浓度比,使发光颜色从黄色转变为黄红色,并实现白光发射.利用该荧光粉与紫外芯片结合制作成白光发光二极管器件,并确定了这些LED器件的发光效率、CIE色度坐标、相关色温(CCT)和显色指数(CRI)等.结果表明,这些荧光粉在紫外激发的白光LED中具有潜在的应用价值.

颜色可调Ca_(2)LaTaO_(6)∶Dy^(3+),Tb^(3+)荧光粉的制备、发光性能及能量传递

本文利用高温固相反应法制备了高效黄绿色多色发光荧光粉Ca_(2)LaTaO_(6)∶Dy^(3+),Tb^(3+),其主要窄发射带来自Tb^(3+)的547 nm处,并且由于Dy^(3+)的敏化作用而在250~400 nm区域具有宽激发带,将Dy^(3+)和Tb^(3+)共掺到Ca_(2)LaTaO_(6)(CLTO)基质中,构建能量传递体系。通过激发/发射光谱及寿命衰减曲线测试证实了Dy^(3+)到Tb^(3+)的能量传递过程。Dy^(3+)→Tb^(3+)的能量传递以偶极-四极相互作用为主,能量传递效率可达80%甚至更高。基于该能量传递过程,在Dy^(3+)的特征激发下,通过改变Dy^(3+)和Tb^(3+)的相对掺杂浓度,可以使发光颜色由黄色渐变为绿色,说明发光颜色可调的多色发光荧光粉Ca_(2)LaTaO_(6)∶Dy^(3+),Tb^(3+)在荧光粉转换的白光LED中具有潜在的应用前景。

SYNTHESIS AND CRYSTAL STRUCTURE OF A NEW COMPOUND Sr_6Sn_2Nb_8O_30

A new compound Sr6Sn2Nb8O30 was found in the ternary system of SrO-SnO2-Nb2O5. The transparent colorless crystal with needle-like shape can be grown by flux method. The crystal structure of new compound was determined by X-ray diffraction, and its belongs to tungsten bronze structure. Sr6Sn2Nb8O30 crystallizes in orthorhombic system with unit cell parameters a= 17. 579 (DA,6= 17. 509(DA,c=7. 7880(5)A,Z = 4 and space group Cmm2.

磷灰石结构Sr_(6)Gd_(4-x)(PO_(4))_(6)Cl_(2):xTb^(3+)的合成和发光性能研究

文章采用高温固相法制备了新型磷灰石结构绿色发光材料Sr_(6)Gd_(4-x)(PO_(4))_(6)Cl_(2):xTb^(3+),研究了这一发光材料的合成温度和烧结时间,得到最佳反应条件。在最佳反应条件的基础上,对Sr_(6)Gd_(4-x)(PO_(4))_(6)Cl_(2):xTb^(3+)系列绿色发光材料的荧光光谱进行分析,得到了Tb^(3+)的最佳掺杂量。

Sr_(7)Zr(PO_(4))_(6):xEu^(2+)蓝色荧光粉的合成及其发光特性

通过高温固相反应合成了新型的蓝色荧光粉Sr_(7)Zr(PO_(4))_(6):xEu^(2+)。通过X射线粉末衍射(XRD)、紫外可见(UV-Vis)吸收光谱、荧光光谱研究了Sr_(7)Zr(PO_(4))_(6):xEu^(2+)材料的相纯度及荧光性质。结果表明,Eu^(2+)掺杂获得的Sr_(7)Zr(PO_(4))_(6):xEu^(2+)荧光粉为纯相,且200-400 nm范围内的近紫外(NUV)光均能对其进行有效的激发。在315 nm的激发下,Sr_(7)Zr(PO_(4))_(6):xEu^(2+)荧光粉发射出峰值位于415 nm左右的蓝光,且Eu^(2+)在Sr_(7)Zr(PO_(4))_(6)基质中的最佳掺杂浓度为0.05,相应的CIE色度坐标为(0.164,0.021),比商用BaMgAl_(10)O_(17)∶Eu^(2+)(BAM)蓝色荧光粉具有更高的色纯度。

Sign reversal of anisotropic magnetoresistance and anomalous thickness-dependent resistivity in Sr_(2)CrWO_(6)/SrTiO_(3) films

High-quality Sr_(2)CrWO_(6)(SCWO) films have been grown on SrTiO_(3)(STO) substrate by pulsed laser deposition under low oxygen pressure. With decrease of the film thickness, a drastic conductivity increase is observed. The Hall measurements show that the thicker the film, the lower the carrier density. An extrinsic mechanism of charge doping due to the dominance of oxygen vacancies at SCWO/STO interfaces is proposed. The distribution and gradient of carrier concentration in SCWO films are considered to be related to this phenomenon. Resistivity behavior observed in these films is found to follow the variable range hopping model. It is revealed that with increase of the film thickness, the extent of disorder in the lattice increases, which gives a clear evidence of disorder-induced localization charge carriers in these films.Magnetoresistance measurements show that there is a negative magnetoresistance in SCWO films, which is considered to be caused by the magnetic scattering of magnetic elements Cr^(3+) and W^(5+). In addition, a sign reversal of anisotropic magnetoresistance(AMR) in SCWO film is observed for the first time, when the temperature varies across a characteristic value, T_(M). Magnetization-temperature measurements demonstrate that this AMR sign reversal is caused by the direction transition of easy axis of magnetization from the in-plane ferromagnetic order at T > T_(M) to the out-of-plane at T < T_(M).

In^(3+)-doped Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)cathode with improved performance for an intermediate-temperature solid oxide fuel cell

Promoting the oxygen reduction reaction(ORR)is critical for commercialization of intermediate-temperature solid oxide fuel cells(IT-SOFCs),where Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)−δ(SFM)is a promising cathode by working as a mixed ionic and electronic conductor.In this work,doping of In^(3+)greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr_(2)Fe_(1.5)Mo_(0.5−x)InxO_(6−δ)(SFMInx),and thus effectively promotes the ORR performance.As a typical example,SFMIn_(0.1)reduces the polarization resistance(R_(p))from 0.089 to 0.046Ω∙cm^(2)at 800°C,which is superior to those doped with other metal elements.In addition,SFMIn0.1 increases the peak power density from 0.92 to 1.47 W∙cm^(−2)at 800°C with humidified H_(2)as the fuel,indicating that In3+doping at the Mo site can effectively improve the performance of SOFC cathode material.

Bismuth doped Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ) double perovskite as a robust fuel electrode in ceramic oxide cells for direct CO_(2)electrolysis

Electrochemical conversion of CO_(2)to CO is an economically feasible method for mitigating greenhouse gas emissions.Among various electrochemical approaches,solid oxide electrolysis cells(SOECs)show high potential for CO_(2)reduction reaction(CO_(2)-RR)due to their ability to operate at high temperatures,resulting in fast reaction kinetics and increased efficiency.Considering their main energy loss is still associated with the large overpotential at the fuel electrode,the development of the highly efficient and durable cathode for SOECs has been extensively searched after.Here,we propose an A-site doping strategy to enhance the properties of Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)(SFM),which improve its performance as a cathode in SOECs for CO_(2)-RR,demonstrating favorable activity and durability.The structural and physiochemical characterizations,together with DFT calculations,show that the partial replacement of Sr by Bi in the SFM double perovskite not only improves CO_(2) adsorption capability at the catalyst surface but also enhances oxygen ionic conduction inside the bulk oxide,resulting in enhanced CO_(2)electrocatalysis performance in SOECs.Specifically,a La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3−δ) (LSGM)electrolyte-supported single cell with the new Bi-doped SFM cathode demonstrates a large current density of 1620 mA cm^(−2) at a cell potential of 1.6 V at 850°C with good operational stability up to 200 h.Bi-doped SFM thus represents a highly promising cathode for ceramic CO_(2)electrolyzers and could accelerate our transition towards a carbon-neutral society.

High-brightness red-emitting double-perovskite phosphor Sr_(2)LaTaO_(6):Eu^(3+) with high color purity and thermal stability[Invited]

Bright Eu3+-activated double-perovskite Sr2LaTaO6 red-emitting phosphors were successfully synthesized by a high-temperature solid-state method. Under near-ultraviolet excitation at 394 nm, optimal Sr2LaTaO6∶0.2 Eu3+phosphors emitted high-brightness red light around 613 nm with the International Commission on Illumination chromaticity coordinates(0.650,0.349). Notably, the color purity can reach 92%. Impressively, the favorable thermal stability of the Sr2LaTaO6∶0.2 Eu3+phosphors was characterized by temperature-dependent emission spectra at different temperatures from 303 to 463 K, and the emission intensity at 423 K remained 73% of its value at 303 K. All of the results suggested that the as-prepared Sr2LaTaO6∶0.2 Eu3+phosphors can be used in near-ultraviolet-excitable white light-emitting diodes as a red-emitting color converter.

Sc掺杂的Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)作为质子导体固体氧化物燃料电池的新型单相阴极

本文利用Sc元素部分取代Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)(SFM)中的Mo,成功制备了具有高质子扩散速率的新型Sc掺杂SFM(SFMSc)材料.理论计算表明,将Sc掺杂到SFM中可以降低材料的氧空位形成能,降低氧化物中质子迁移的能垒,并提高材料氧还原反应的催化活性.使用单相SFMSc阴极的质子导体固体氧化物燃料电池(H-SOFC)比使用不含Sc的SFM单相阴极电池具有更高的电池性能,其在700℃时的性能达到1258 mW cm^(−2).该性能也超过了许多其他使用单相无钴阴极的HSOFC.此外,材料良好的电化学性能并没有以牺牲其稳定性为代价.SFMSc材料在含CO_(2)的气氛中以及在燃料电池工作条件下都表现出良好的稳定性.高输出性能和良好的稳定性,使SFMSc成为一种有潜力的高效的H-SOFC阴极材料.

高效宽带近红外发光材料Sr_(2)ScSbO_(6):Cr^(3+)及其在类太阳光源中的应用

类太阳光光源包含可见光和近红外(NIR)光,在健康照明等领域具有重要的应用.然而众多应用却由于目前缺乏具有高效率和高发光热稳定的900 nm附近的NIR发光材料而受到限制.在此,我们报道了一种具有双钙钛矿型结构的宽带NIR荧光粉Sr_(2)ScSbO_(6):Cr^(3+),其具有高发光效率和良好的发光热稳定性.在550 nm光激发下,该材料具有以~890 nm为中心的宽带NIR发射,发光内/外量子效率分别为82.0%/35.7%.此外,材料显示出优良的发光热稳定性,在430 K下的发光积分强度保持初始强度的66.4%.结合465 nm蓝光芯片和其他商用荧光粉,我们成功制作了荧光粉转换发光二极管器件,呈现出从蓝色到近红外光的相对完整的类太阳光谱,有望用于日常照明和类太阳光谱发光器件.

Study on the Different Photocatalytic Performances for Tetracycline Hydrochloride Degradation of p-block Metal Composite Oxides Sr_(1.36)Sb_(2)O_6 and Sr_(2)Sb_(2)O_7

p-block metal composite oxides Sr_(1.36)Sb_(2)O_(6) and Sr_(2)Sb_(2)O_(7) synthesized by a hydrothermal method as photocatalysts in the degradation of tetracycline hydrochloride under UV light irradiation have been extensively studied.The effects of synthesis conditions on the photocatalytic activity were discussed.The Sr_(1.36)Sb_(2)O_(6)-100°C-24 h-5 and Sr_(2)Sb_(2)O_(7)-150℃-24 h^(-2) samples prepared under optimal conditions exhibited remarkably different photocatalytic activities.The essential factors influencing the difference of photocatalytic performance were revealed.The results showed that the different photocatalytic activities observed for Sr_(1.36)Sb_(2)O_(6)and Sr_(2)Sb_(2)O_(7) could be attributed to their different electronic and crystal structures.Our work will provide a new perspective for the screening and design of p-block metal composite oxide photocatalysts to enhance the removal of organic pollutants in the environment.

High-temperature ferromagnetic metallic phase in LaMnO_(3)/Sr_(3)Al_(2)O_(6)heterostructure

To achieve a flexible single-crystal multifunctional membrane,the freestanding process of a rigid epitaxial transition metal oxide thin film via a buffered water-dissolution sacrificial layer has attracted reasonable attentions.Owing to the difference in chemical potential,specific element affinity,and lattice constant between the target membrane and the sacrificial layer,the freestanding process may cause an indelible change of physics property once the target thin film is sensitive to the above factors.Here,the heterostructures composed of the generally adopted sacrificial layer Sr_(3)Al_(2)O_(6)(SAO)and LaMnO_(3)(LMO)have been systematically investigated.The electrical and magnetic properties of LMO show extreme sensitivity to the thickness of SAO(tSAO).Then we have also found that LMO/SAO heterostructures can exhibit the coexistence of two ferromagnetic phases,the significantly enhanced Curie temperature~342 K,and the large magnetoresistance-23.3%at 300 K,which is similar to the optimal-doped manganite such as La_(2/3)Sr_(1/3)MnO_(3).X-ray diffraction results show that continuously tunable strain from out-of-plane tension to relaxation and then to compression can be generated by adjusting tSAO.This strain can stabilize the migrated oxygen from LMO to SAO,which is induced by the large oxygen affinity difference between Bsite Mn and Al.It is believed that these unexpected electrical/magnetic phenomena are originated from the combined effects of interfacial element diffusion and strain.Our study provides a strategy for designing new magnetic phases,and a reference for the fundamental understanding of strongly correlated transition metal oxide systems in the freestanding process.

A novel sol–gel route to synthesize(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) ceramics with enhanced electrocaloric effect

(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) ultra-fine powders were synthesized by a novel sol–gel route,and the mechanism of the reaction was discussed.SrCO_(3),BaCO_(3),oxalate niobium and citric acid were used to initiate the sol–gel process,and ethylene glycol(EG)was added to further polymerize the cross-linking structure.The evolution of the(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) phase,the reaction process and the microstructures were investigated by X-ray diffraction(XRD),Raman spectroscopy,Fourier transform infrared spectroscopy,DSC-TG and scanning electron microscopy.The synthesis temperature of the(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) powders reached as low as 1200℃,and the size and morphology of the powders were controlled by temperature.By adjusting the calcination temperature,we obtained(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) powders with uniform sizes of 20 nm to 500 nm.Then,dense(Sr_(0.5)Ba_(0.5))Nb_(2)O_(6) ceramics were successfully prepared using these ultrafine powders.Finally,an enhanced electrocaloric effect(ECE)value of 0.35℃ was obtained at 100 kV/cm.