Sr2GaScO5, Sr10Ga6Sc4O25, and SrGa0.75Sc0.25O2.5: a play in the octahedra to tetrahedra ratio in oxygen-deficient perovskites

Three different perovskite-related phases were isolated in the SrGa(1-x)Sc(x)O(2.5) system: Sr(2)GaScO(5), Sr(10)Ga(6)Sc(4)O(25), and SrGa(0.75)Sc(0.25)O(2.5). Sr(2)GaScO(5) (x = 0.5) crystallizes in a brownmillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) ?, b = 15.1594(1) ?, and c = 5.70926(4) ?] with complete ordering of Sc(3+) and Ga(3+) over octahedral and tetrahedral positions, respectively. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4(1)/a, a = 17.517(1) ?, c = 32.830(3) ?]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) can be described as a stacking of eight perovskite layers along the c axis ...[-(Sc/Ga)O(1.6)-SrO(0.8)-(Sc/Ga)O(1.8)-SrO(0.8)-](2).... Similar to Sr(2)GaScO(5), this structure features a complete ordering of the Sc(3+) and Ga(3+) cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr(10)Ga(6)Sc(4)O(25) is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc(3+) by Ga(3+) leads to the formation of the cubic perovskite phase SrGa(0.75)Sc(0.25)O(2.5) (x = 0.25) with a = 3.9817(4) ?. This compound incorporates water molecules in the structure forming SrGa(0.75)Sc(0.25)O(2.5)·xH(2)O hydrate, which exhibits a proton conductivity of ～2.0 × 10(-6) S/cm at 673 K.     

Li2O-Al2O3-GeO2-P2Os微晶玻璃的微观结构和离子电导率

采用传统熔体冷却法制备了Li3-xAl2-xGex(PO4)3(x=1.1～1.9)体系玻璃,并通过热处理工艺获得了高电导率的微晶玻璃.通过XRD、TEM和交流阻抗等测试方法,研究了该系微晶玻璃的物相组成、微观形貌和锂离子电导率.结果表明:该系统微晶玻璃析出导电主晶相为LiGe2(PO4)3,杂质相为AlPO4和GeO2.当x=1.5时,由于导电主晶相LiGe2(PO4)3晶粒充分长大、分布均匀,所制备微晶玻璃的室温锂离子电导率最高(5.72×10-4 S·cm-1),可以满足全固态锂离子电池对电解质高室温电导率的要求.     

Li2O-Al2O3-GeO2-P2O5微晶玻璃的微观结构和离子电导率

采用传统熔体冷却法制备了Li3-xAl2-xGex(PO4)3(x=1.1~1.9)体系玻璃,并通过热处理工艺获得了高电导率的微晶玻璃。通过XRD、TEM和交流阻抗等测试方法,研究了该系微晶玻璃的物相组成、微观形貌和锂离子电导率。结果表明:该系统微晶玻璃析出导电主晶相为LiGe2(PO4)3,杂质相为AlPO4和GeO2。当x=1.5时,由于导电主晶相LiGe2(PO4)3晶粒充分长大、分布均匀,所制备微晶玻璃的室温锂离子电导率最高(5.72×10-4 S.cm-1),可以满足全固态锂离子电池对电解质高室温电导率的要求。     

Ba12Y4.67Ti8O35的交流阻抗谱和氧浓差电势测量

用高温固体合成法制备了经验分子式为Ba12Y4.67Ti8O35的导电陶瓷.利用交流阻抗谱技术、氧浓差电势测量和热电效应测量等方法表征了材料的导电性能.研究指出, 该材料是一种氧离子/空穴混合导体.在700 ℃下，材料本体的电导约为2×10－3 Ω－1•cm－1，氧离子迁移数为0.35.对700 ℃下空气、O2和N2气氛中的交流阻抗谱数据进行了等效电路拟合.拟合指出，在空气和O2气氛中，氧离子的扩散阻抗谱不能明显地观察到是因为氧离子电导通路被空穴电导短路；而在N2气氛中，阻抗谱在低频段表现出特征的扩散阻抗.     

Oxygen surface exchange kinetics of SrTi(1-x)Fe(x)O(3-δ) mixed conducting oxides

The oxygen surface exchange kinetics of mixed conducting perovskite oxides SrTi(1-x)Fe(x)O(3-δ) (x = 0, 0.01, 0.05, 0.35, 0.5) has been investigated as a function of temperature and oxygen partial pressure using the pulse-response (18)O-(16)O isotope exchange (PIE) technique. Arrhenius activation energies range from 140 kJ mol(-1) for x = 0 to 86 kJ mol(-1) for x = 0.5. Extrapolating the temperature dependence to the intermediate temperature range, 500-600 °C, indicates that the rate of oxygen exchange, in air, increases with increasing iron mole fraction, but saturates at the highest iron mole fraction for the given series. The observed behavior is concomitant with corresponding increases in both electronic and ionic conductivity with increasing x in SrTi(1-x)Fe(x)O(3-δ). Including literature data of related perovskite-type oxides Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ), La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-δ), La(0.6)Sr(0.4)CoO(3-δ), and Sm(0.5)Sr(0.5)CoO(3-δ), a linear relationship is observed in the log-log plot between oxygen exchange rate and oxide ionic conductivity with a slope fairly close to unity, suggesting that it is the magnitude of the oxide ionic conductivity that governs the rate of oxygen exchange in these solids. The distribution of oxygen isotopomers ((16)O(2), (16)O(18)O, (18)O(2)) in the effluent pulse can be interpreted on the basis of a two-step exchange mechanism for the isotopic exchange reaction. Accordingly, the observed power law dependence of the overall surface exchange rate on oxygen partial pressure turns out to be an apparent one, depending on the relative rates of both steps involved in the adopted two-step scheme. Supplementary research is, however, required to elucidate which of the two possible reaction schemes better reflects the actual kinetics of oxygen surface exchange on SrTi(1-x)Fe(x)O(3-δ).     

First total H+/Li+ ion exchange in garnet-type Li5La3Nb2O12 using organic acids and studies on the effect of Li stuffing

Garnet-type Li(5+x)Ba(x)La(3-x)Nb(2)O(12) (x = 0, 0.5, 1) was prepared using a ceramic method, and H(+)/Li(+) ion exchange was performed at room temperature using organic acids, such as CH(3)COOH and C(6)H(5)COOH, as proton sources. Thermogravimetric analysis showed that H(+)/Li(+) ion exchange was nearly (100%) completed using the x = 0 member with CH(3)COOH, while it proceeded to about 40% for x = 0.5 and 13% for x = 1. In C(6)H(5)COOH, proton exchange proceeded to about 82% for x = 0, ～40% for x = 0.5, and ～25% for x = 1. Similar proton-exchange trends were reported in H(2)O, where ion exchange occurs more readily for garnets with lower Li content in Li(5+x)Ba(x)La(3-x)Nb(2)O(12), that is, when excess Li ions preferentially reside in the tetrahedral sites of the garnet structure.     

Structural and spectroscopic properties of pure and doped Ba6Ti2Nb8O30 tungsten bronze

Pure and doped Ba(6)Ti(2)Nb(8)O(30) (BTN), obtained by substituting M = Cr, Mn, or Fe on the Ti site (Ba(6)Ti(2-x) M(x)Nb(8)O(30), x = 0.06 and 0.18) and Y and Fe on the Ba and Ti sites, respectively (Ba(6-x)Y(x)Ti(2-x)Fe(x)Nb(8)O(30), x= 0.18), are synthesized. The influence of cation doping on the local structure, the cation oxidation state, and the possible defect formation able to maintain the charge neutrality are investigated by spectroscopic (electron paramagnetic resonance (EPR) and micro-Raman), structural (X-ray powder diffraction) and transport (impedance spectroscopy, thermoelectric power) measurements, in the temperature range of 300-1200 K in air and N(2) flow. Starting from the valence state of the doping ions (Fe(3+), Cr(3+), and Mn(2+)), determined by EPR, and from thermoelectric power measurements, evidencing a negative charge transport, different charge-compensating defect equilibria, based on the creation of positive electron holes or oxygen vacancies and electrons, are discussed to interpret the conductivity results.     

Synthesis, structure, chemical stability, and electrical properties of Nb-, Zr-, and Nb-codoped BaCeO3 perovskites

We report the effect of donor-doped perovskite-type BaCeO(3) on the chemical stability in CO(2) and boiling H(2)O and electrical transport properties in various gas atmospheres that include ambient air, N(2), H(2), and wet and dry H(2). Formation of perovskite-like BaCe(1-x)Nb(x)O(3±δ) and BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) (x = 0.1; 0.2) was confirmed using powder X-ray diffraction (XRD) and electron diffraction (ED). The lattice constant was found to decrease with increasing Nb in BaCe(1-x)Nb(x)O(3±δ), which is consistent with Shannon's ionic radius trend. Like BaCeO(3), BaCe(1-x)Nb(x)O(3±δ) was found to be chemically unstable in 50% CO(2) at 700 °C, while Zr doping for Ce improves the structural stability of BaCe(1-x)Nb(x)O(3±δ). AC impedance spectroscopy was used to estimate electrical conductivity, and it was found to vary with the atmospheric conditions and showed mixed ionic and electronic conduction in H(2)-containing atmosphere. Arrhenius-like behavior was observed for BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) at 400-700 °C, while Zr-free BaCe(1-x)Nb(x)O(3±δ) exhibits non-Arrhenius behavior at the same temperature range. Among the perovskite-type oxides investigated in the present work, BaCe(0.8)Zr(0.1)Nb(0.1)O(3±δ) showed the highest bulk electrical conductivity of 1.3 × 10(-3) S cm(-1) in wet H(2) at 500 °C, which is comparable to CO(2) and H(2)O unstable high-temperature Y-doped BaCeO(3) proton conductors.     

BaCe_(0.8-x)Nb_xGd_(0.2)O_(3-δ)(0≤x≤0.45)的制备及性能研究

采用高温固相反应法制备了质子导体BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)。结合XRD、SEM、EIS等技术对其物相、微观形貌、稳定性及电导率进行了研究。结果表明,在1600℃烧结5h制备的质子导体BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)均能保持主相为斜方晶的钙钛矿结构。Nb的加入可明显提高烧结样品的致密性及在CO2和水蒸气气氛下的稳定性。在湿润H2/Ar(0.4%,V/V)气氛中800℃下,x=0.1样品的电导率为5.73mS·cm-1,电导活化能为0.35eV,与x=0的样品相当。     

Epitaxial thin films of ATiO(3-x)H(x) (A = Ba, Sr, Ca) with metallic conductivity

Epitaxial thin films of titanium perovskite oxyhydride ATiO(3-x)H(x) (A = Ba, Sr, Ca) were prepared by CaH(2) reduction of epitaxial ATiO(3) thin films deposited on a (LaAlO(3))(0.3)(SrAl(0.5)Ta(0.5)O(3))(0.7) substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO(3)/LSAT thin film hydridized at 530 °C for 1 day had hydride concentration of 4.0 × 10(21) atoms/cm(3) (i.e., SrTiO(2.75)H(0.25)). The electric resistivity of all the ATiO(3-x)H(x) films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO(3-x)H(x) powder, revealing that ATiO(3-x)H(x) are intrinsically metallic, with high conductivity of 10(2)-10(4) S/cm. Treatment with D(2) gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials' inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible.     

SiO44-对Li3Sc2(PO4)3快离子导体的阴离子替代效果研究

Li3Sc2(PO4)3因具有有利的离子传导通道、低的电子电导率和高的稳定性而成为全固态锂离子电池用固体电解质最具竞争力的材料之一,然而这一化合物只有在245℃以上的γ相才具有快离子传导特性。人们主要采用Zr4+、Ti4+等阳离子部分取代其中的Sc3+以改善材料的室温电导率,有关该化合物PO43-阴离子替代的报道还很少。本研究试图利用机械研磨技术,通过向Li3Sc2(PO4)3原料混合物中加入适量SiO2,以期能够实现对该化合物的部分阴离子替代。研究结果表明:所制备的Li3+xSc2(PO4)3-x(SiO4)x(x=0~0.6)系列化合物在x=0.15时电导率达到最大值,σ298=9.55×10-4 S.m-1,离子传导激活能达到最小值45.06 kJ.mol-1。29Si MAS-NMR测试结果证实所加入的SiO2主要以[SiO4]四面体形式存在替代Li3Sc2(PO4)3中部分[PO4]四面体。     

单相Ce0.5Zr0.5O2立方固溶体的高压高温合成

以化学沉淀法制备的 Ce O2 和 Zr O2 纳米微粒为前驱体 ,首次在高压高温 (3 .1 GPa,1 0 73 K)下合成了单相 Ce0 .5Zr0 .5O2 面心立方固溶体 .使用 X射线衍射、TG-DTA、XPS、Raman、电子自旋共振谱和交流阻抗谱等对样品的结构、Ce离子的价态和导电性进行了表征 .实验结果表明 ,纳米 Ce O2 -50 % Zr O2 混合物在高压 (0 .9GPa以上 )高温 (1 0 73 K以上 )条件下可以发生固态反应 ,高压下固溶温度明显降低 .Ce0 .5Zr0 .5O2 面心立方固溶体在 773 K以下是热稳定的 ,不发生结构转变 ,固溶体中 Ce离子完全以 Ce4 + 形式存在 ,773 K退火也不引起 Ce4 + 向 Ce3 + 转变 ,晶格中氧缺位非常少 .Ce0 .5Zr0 .5O2 面心立方固溶体是离子导电 ,82 3 K时电导率 σ=1 .2× 1 0 -5S/cm,与纯 Ce O2 在同温度下的电导率同数量级 ;1 1 2 3 K时 σ=2 .1× 1 0 -3 S/cm,小于掺入稀土或碱土氧化物的氧化锆和氧化铈基电解质的电导率 .在高温区和低温区 ln(σT)与 1 /T的关系满足斜率不同的二条直线 ,低温活化能小于高温活化能 .固溶体的显微硬度 (50 g载荷 )为 572 HV.     

Syntheses，Structures and Properties of Some New Composition Perovskite Compounds：Sr_（0．6）Bi_（0．4）FeO_（2．7），Sr_（1－x）Bi_xFeO_（3－y） and Ba_（1．5）Pt_（0．5）Mn_2O_6

Ｓｙｎｔｈｅｓｅｓ，ＳｔｒｕｃｔｕｒｅｓａｎｄＰｒｏｐｅｒｔｉｅｓｏｆＳｏｍｅ　ＮｅｗＣｏｍｐｏｓｉｔｉｏｎＰｅｒｏｖｓｋｉｔｅＣｏｍｐｏｕｎｄｓ：Ｓｒ_（０．６）Ｂｉ_（０．４）ＦｅＯ_（２．７），Ｓｒ_（１－ｘ）Ｂｉ_ｘＦｅＯ_（３－ｙ）　ａｎｄ　Ｂａ...     

Role of B-site ion on proton conduction in acceptor-doped Sm2B2O(7-δ) (B = Ti, Sn, Zr and Ce) pyrochlores and C-type compounds

Proton conduction in three pyrochlores, Sm(1.92)Ca(0.08)B(2)O(7-δ), B = Ti, Sn, Zr and one phase with a related C-type fluorite superstructure, B = Ce, has been investigated. The samples were prepared by solid state reaction. Infrared spectroscopy measurements and thermogravimetric analysis were carried out to study the extent of proton dissolution and determine its dependence on the B-site ion. Electrochemical impedance spectroscopy, performed on heating and cooling pre-hydrated samples, confirmed significant levels of proton conduction for Sm(1.92)Ca(0.08)Ti(2)O(7-δ) and Sm(1.92)Ca(0.08)Sn(2)O(7-δ) up to T～ 500 °C. In comparison the B = Zr and Ce samples revealed lower levels of proton conductivity, confined to temperatures below ～ 400 °C. Proton diffusion coefficients of 3.36 × 10(-8), 1.73 × 10(-9), 5.53 × 10(-10) and 2.78 × 10(-11) cm(2) s(-1) were determined at 300 °C for samples with B = Ti, Sn, Zr and Ce respectively. The proton mobility of Sm(1.92)Ca(0.08)Ti(2)O(7-δ) is therefore approximately one order of magnitude lower than that found in yttrium-doped perovskite phases such as BaZrO(3) and BaCeO(3).     

On the influence of strain on ion transport: microstructure and ionic conductivity of nanoscale YSZ|Sc2O3 multilayers

Multilayer samples of the type (YSZ|Sc2O3) × n with layer thicknesses between 8 nm (n=100) and 250 nm (n=5) were prepared on (0001) sapphire substrates by pulsed laser deposition (PLD). The samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM/HRTEM, SAED (selected-area electron diffraction) and quantitative EELS (electron energy-loss spectroscopy)). The polycrystalline layers show a columnar microstructure, which is typical for the used preparation technique. The layers are highly textured and only one axial orientation relation is found between yttria-stabilised zirconia (YSZ), scandium oxide and the substrate: (0001) Al2O3‖(111) Sc2O3‖(111) YSZ. A preferred orientation relationship also exists for the azimuthal rotation of the crystallites, which was demonstrated by SAED, XRD pole figure measurements and fast Fourier transformation (FFT) of HRTEM micrographs. The interfaces between YSZ, Sc2O3 and the substrate are sharp and do not contain diffuse transition regions. Dislocations appear not to be arranged in regular arrays. With increasing interface density (thinner individual layers in the multilayer), the conductivity of the multilayers decreases. We relate this to the negative nominal misfit present at the YSZ|Sc2O3 interfaces (compressive stress in YSZ at the phase boundaries). This observation agrees well with the previously investigated case of YSZ|Y2O3 (A. Peters et al., Phys. Chem. Chem. Phys., 2008, 10, 4623), where tensile misfit strain was present in YSZ at the phase boundaries, leading to a conductivity increase.     

新钽酸盐Ba2LnTi2Ta3O15(Ln=Y、La)的结构与介电性能

通过固相反应法合成了四方钨青铜结构新钽酸盐Ba2LaTi2Ta3O15与Ba2YTi2Ta3O15,分别进行了X射线衍射分析与介电性能测试.结果表明, Ba2LaTi2Ta3O15室温时晶胞参数为a=1.242 64(5) nm, c=0.391 57(2) nm,为四方钨青铜结构顺电相；Ba2YTi2Ta3O15室温时晶胞参数为a=1.236 46(4) nm, c=0.388 60(2) nm,为四方钨青铜结构铁电相,铁电相与顺电相转变温度为180 ℃.频率为1 MHz时, Ba2LaTi2Ta3O15陶瓷的室温相对介电常数为194,介电损耗也降低至8×10－4. Ba2YTi2Ta3O15陶瓷的室温相对介电常数为107.     

Effect of fluorine doping on the ionic (O2−, H+) conductivity of oxygen-deficient complex oxides

Russian Chemical Bulletin - The effect of fluorine doping on the transport properties (oxygen-ion and proton conductivity) of perovskite-related complex oxides Ba2In2O5, Ba4In2Zr2O11, and...     

LaCo(1-x)Ni(x)O(3) with Improved Electrical Conductivity

To determine the applicability of LaCo(1-x)Ni(x)O(3) in a conductive material for electrical wiring, the dependence of the electronic transport property on the Ni content is investigated via Hall effect measurements, Rietveld analyses, and band-structure calculations. Ni doping (50 mol %) into the Co sites realizes a high electrical conductivity of 1.9 × 10(3) S/cm, which is an unexpectedly high value for a LaCo(1-x)Ni(x)O(3) system, at room temperature due to the high carrier concentration of 2.2 × 10(22) cm(-3) and the small effective mass of 0.1 m(e). In addition, the high electrical conductivity is maintained from room temperature to 900 °C; that is, the temperature coefficient of the conductivity is smaller than that of standard metals. Thus, the results indicate that LaCo(0.5)Ni(0.5)O(3) is suitable as a conductive material for electrical wiring at high temperatures in air.     

Solvate-supported proton transport in zeolites.

Solvate-supported proton transport in zeolite H-ZSM-5 was studied by means of complex impedance spectroscopy. The zeolite shows enhanced proton mobility in the presence of NH3 and H2O that depends on the concentration of the solvate molecule, temperature (298-773 K), and the SiO2/Al2O3 ratio of the zeolite (30-1000). In general, proton conductivity in H-ZSM-5 is most effectively supported in the presence of NH3 and H2O at high concentrations, low temperatures, and low SiO2/Al2O3 ratios (< or = 80). For the aluminum-rich samples desorption measurements reflect different transport mechanisms that depend on the respective temperature range. Up to about 393 K a Grotthus-like proton transport mechanism is assumed, whereas at higher temperatures (393-473 K) vehiclelike transport seems to dominate. The activation energies for NH4+ and H3O+ vehicle conductivity depend on the SiO2/Al2O3 ratio, and the values are in the range of 49-59 and 39-49 kJ mol-1, respectively, and thus significantly lower than those for "pure" proton conduction in solvate-free samples.     

Cation mobility and kinetics of ion exchange in zirconium hydrogen monothiophosphate hydrate, Zr(HPO(3)S)(2)x1.5H(2)O

The ion conductivity of zirconium hydrogen monothiophosphate (Zr(HPO(3)S)(2)x1.5H(2)O) has been measured by impedance spectroscopy. The measured value of proton conductivity is 3 x 10(-5) S/cm at 298 K. Conductivity was shown to decrease with increasing temperature due to a dehydration process. Above 450 K, the conductivity is likely governed by proton transport in the anhydrous phase Zr(HPO(3)S)(2). The activation energies of proton conductivity were measured to be 18 +/- 2 kJ/mol for Zr(HPO(3)S)(2)x1.5H(2)O and 60 +/- 3 kJ/mol for the anhydrous compound. The kinetics of ion exchange was studied with the use of potentiometric titration for several ion pairs, H(+)/Na(+), H(+)/Zn(2+), and Na(+)/Zn(2+) in Zr(HPO(3)S)(2)x1.5H(2)O. The diffusion coefficient values for H(+)/Na(+) ion exchange in Zr(HPO(3)S)(2)x1.5H(2)O are lower than those reported in alpha-zirconium phosphate. At the same time, the mobility of zinc ions in Zr(HPO(3)S)(2)x1.5H(2)O is higher than sodium ion mobility. The ion exchange H(+)/Zn(2+) is accompanied by the slow hydrolysis of the initial compound. In all cases, the powdered solids were evaluated by powder X-ray diffraction, and particle sizes were controlled by grinding and sieving the powders.