Yttrium-doped Strontium Titanate Research Articles

Deposition of NiO on 3 mol% yttria-stabilized zirconia and Sr0.96Y0.04TiO3 materials by impregnation method

The main purpose of this work was the synthesis of composite materials by deposition of nickel oxide on 3 mol% yttria-stabilized zirconia (3 mol% Y2O3–97 mol% ZrO2–YSZ) and Sr0.96Y0.04TiO3 (4 mol% Y-doped strontium titanate—SYTO) supports. Yttria-stabilized zirconia and yttrium-doped strontium titanate were obtained by modified citrate method. The deposition of nickel oxide was performed by impregnation method. All materials were impregnated with proper amount of nickel(II) nitrate aqueous solution to receive the 1 and 5 mass% of nickel in the final composite. The temperature-programmed reduction (TPR) was applied to analyze the reduction mechanism of deposited NiO. Three forms of nickel oxide: non-stoichiometric NiO1+x, hexagonal and cubic are postulated on the base of the TPR profiles and analysis of bonds length in nickel oxides structures. Moreover, TPR analysis shows that support strongly affects the reduction mechanism as a consequence of various interactions between NiO and YSZ/SYTO. In the case of YSZ, the nickel oxide reveals the tendency to deposit on the support surface, while using SYTO as the support, nickel oxide exhibits significant ability to react with doped strontium titanate and what is more important nickel incorporates into Sr0.96Y0.04TiO3 structure.

Evidence of the pressure-induced conductivity switching of yttrium-doped SrTiO3

The electrical transport properties of undoped and yttrium-doped strontium titanate (Sr(Ti1 – xYx)O3 – δ, x = 0, 0.02) under high pressure were investigated with in situ impedance spectroscopy measurements. A pressure-induced conductivity switching for undoped and 2 mole% Y-doped strontium titanate is observed at around ~10.0 and 7.0 GPa respectively, which are caused by a cubic to tetragonal I4/mcm phase transition. The decrease of the phase transition point of 2 mole% Y-doped strontium titanate can be attributed to larger Y3+ atoms occupying the B-site and the creation of more oxygen vacancies, which lead to octahedra tilting and symmetry breaking. The results of the voltage-bias dependence of grain-boundary impedance of undoped and 2 mole% Y-doped strontium titanate at different pressures revealed that Schottky-type potential barriers formed at grain boundaries are the key factor for the accumulation of oxygen vacancy at the interface under pressure.

Synthesis, microstructural properties and chemical stability of 3DOM structures of Sr1−xYxTiO3

Yttrium-doped strontium titanate is a perovskite with a great potential to act as an anode material for solid oxide fuel cells. Two different synthesis procedures have been used to modify and optimize perovskite morphology. First way involved usage of surfactant TX-100 and led to obtainment of irregular structure with pore diameter of 150–200 nm, whereas in the second one, spheres of poly (methyl methacrylate) acted as soft templates and led to attainment of highly regular hollow perovskite network with pore diameter of around 110 nm. The discussion concerning the influence of yttrium on thermal properties of material, thermal expansion coefficients and chemical stability (in water–carbon dioxide rich atmosphere) were presented. It was found that introduction of yttrium into the strontium titanate leads to the decrease of SrTiO3 shrinkage temperature. Moreover, coupling TG measurements with mass spectrometry allowed to determinate behavior of pure and yttrium-doped strontium titanate in H2O and CO2 containing atmosphere. It was observed that addition of yttrium into SrTiO3 has no influence on materials stability.

Exploring strontium titanate as a reforming catalyst for dodecane

Yttrium-doped strontium titanate (YST)-based perovskite has been explored as catalyst for reforming dodecane. Active metal elements such as ruthenium, nickel and cobalt were doped on the B-site of the perovskite to boost the catalyst activity. Commercial Ni–alumina catalyst has been used for benchmarking. Both steam and autothermal reforming schemes have been used at 800 and 850 °C. Irrespective of the doping elements, all catalysts performed well and had comparable activity and conversion as the commercial catalyst with slight advantage for ruthenium followed by nickel-based catalysts. Hydrogen and syngas yields fall into the range of 65–75 and 83–91 %, respectively. Conversion was consistently between 84 and 90 %. As such, the YST-based perovskite is a promising catalyst for reforming of heavy liquid hydrocarbon fuel.

Microstructural and electrical properties of Y0.07Sr0.93-x TiO3-δ perovskite ceramics

Abstract In order to find a relationship between electrical and microstructural properties, yttrium-doped strontium titanate (7 mol%) with various values of strontium nonstoichiometry was investigated and shown in this work. It has been observed that yttrium doping can affect the electrical properties of SrTiO3 to a great extent. Moreover, the microstructural and electrical properties can be influenced by strontium nonstoichiometry. The defect chemistry explaining obtained results was also suggested and discussed.

Life Cycle Analysis of Ceramic Anode-Supported SOFC System Manufacturing Processes

The environmental impact of manufacturing an yttrium-doped strontium titanate (SYT) anode-supported planar solid oxide fuel cell (SOFC) system has been examined. Key components of an SOFC system including anode substrate, PEN (Positive electrode-Electrolyte-Negative electrode) structure, interconnects, and balance of plant (BoP) have been evaluated in terms of energy consumption and key air emissions using the Life Cycle Analysis (LCA) approach.

Effect of Addition of Titanium Nitride on Thermoelectric Performance of Yttrium-Doped Strontium Titanate

We examined the effect of addition of titanium nitride on thermoelectric performance of this material. The samples constructed of Y-doped SrTiO3 and TiN were prepared by two steps of the solid-state reactions. SrTiO3 with cubic perovskite structure was formed in all samples. The highest electric conductivity was found for Sr0:9Y0:1TiO3-0.1TiN, whereas the largest absolute value in Seebeck coefficient was found for Sr0:9Y0:1TiO3. Lower thermal conductivity was found for Sr0:9Y0:1TiO3-0.1TiN. The ZT was calculated from the electric conductivity, the Seebeck coefficient, and the thermal conductivity. A high performance was shown in Sr0:9Y0:1TiO3-0.1TiN, giving a high electric conductivity and a low thermal conductivity simultaneously. The highest value of ZT was obtained to be 0.26 at 1077 K for this sample.

Preparation and electrical properties of yttrium-doped strontium titanate with B-site deficiency

Yttrium-doped strontium titanate with B-site deficiency (Y 0.08Sr 0.92Ti 1− x O 3− δ ) is synthesized via conventional solid-state reaction. The effect of B-site deficiency on the lattice parameter, sinterability, microstructure and electrical properties of Y 0.08Sr 0.92TiO 3− δ is investigated. The charge compensation mechanism for B-site deficiency is proposed. The limit of B-site deficiency in Y 0.08Sr 0.92Ti 1− x O 3− δ is below 5 mol % in Ar with 5% H 2 at 1500 °C. The sinterability of Y 0.08Sr 0.92Ti 1− x O 3− δ decreases slightly with increasing deficiency level ( x). Compared with Y 0.08Sr 0.92TiO 3− δ , the electrical conductivity of Y 0.08Sr 0.92Ti 1− x O 3− δ samples decreases while the ionic conductivity increases with increasing B-site deficient amount. It is assumed that the deficiency of Ti in Y 0.08Sr 0.92Ti 1− x O 3− δ is charge compensated by the increase of oxygen vacancy concentration and the decrease of Ti 3+ concentration. Y 0.08Sr 0.92Ti 1− x O 3− δ shows a relatively stable electrical conductivity at different oxygen partial pressures and displays an excellent chemical compatibility with YSZ electrolyte below 1200 °C.

Operation of an LSGMC Electrolyte-Supported SOFC with Composite Ceramic Anode and Cathode

An all-perovskite-based intermediate-temperature fuel cell was fabricated from materials synthesized using glycine-nitrate process (GNP) combustion synthesis and modified Pechini synthesis routes. Yttrium-doped strontium titanate (SYT) was chosen as the conductive ceramic anode component to avoid problems associated with Ni-based anodes. La0.8 Sr0.2 Ga0.8 Mg0.1 Co0.1 O3-δ electrolyte-supported solid oxide fuel cells (SOFCs) with composite ceramic anode and cathode exhibit a relatively high power density of 0.246 Wcm at 800°C at 0.5 V. © 2007 The Electrochemical Society.

Effect of fabrication parameters on the electrical conductivity of Y xSr 1−xTiO 3 for anode materials

Yttrium-doped strontium titanate (Y x Sr 1− x TiO 3), as probable anode material for SOFC, was prepared by solid-state reaction. The solubility of yttrium in SrTiO 3 at different temperatures was examined and the electrical conductivities of Y x Sr 1− x TiO 3 were measured from 500 to 1000 °C. The effects of doping amount, fabrication atmosphere, and sintering temperature on the electrical conductivity of Y x Sr 1− x TiO 3 were investigated. Y x Sr 1− x TiO 3 with x = 0.08 was found to give the maximum electrical conductivity, 71 S/cm at 800 °C in pure hydrogen. Reducing atmospheres and appropriate sintering temperatures play a positive role in improving the electrical conductivity.

Effect of ceria on properties of yttrium-doped strontium titanate ceramics

This work reports the preparation and properties of the ceramic mixtures of the A-site deficient perovskite Sr 0.94Y 0.04TiO 3 (SYT) with CeO 2 in a range of ratios with a view to establishing their potential as anode materials for solid oxide fuel cells. Good electrical conductivity that decreased with increasing CeO 2 content was observed on reduction in forming gas. The composition with 50 wt.% of CeO 2 showed the conductivity of 7.0 S/cm at 900 °C in forming gas. The thermal expansion of SYT–CeO 2 ceramics in forming gas and in air were investigated in the range 25–900 °C at a ramping rate of 3 °C/min and thermal expansion coefficients were determined. The addition of ceria was found to have a positive influence on the catalytic behavior of SYT–CeO 2 ceramics towards steam methane reforming.

Electrical Properties of Yttrium-Doped Strontium Titanate under Reducing Conditions

The electrical conductivity of containing rare earth dopants (Y, La, Pr, Sm, Nd, Gd, or Yb) was measured at 600-900°C in reducing atmospheres. An unusually high conductivity was observed for the yttrium-doped samples compared to those with rare earth dopants, particularly at the composition of the solubility limit where the conductivity at 800°C was 64 S/cm. The conductivity was confirmed to be n-type by thermopower measurements. The oxygen deficiency was determined to be 1% by thermogravimetric analysis. Increasing the strontium vacancy concentration to effected a further improvement in conductivity to 82 S/cm. This material has high structural stability over a broad range of temperature (up to 1400°C) and oxygen partial pressure A simple defect model was developed to explain the change of electrical conductivity as a function of yttrium content and oxygen deficiency. © 2001 The Electrochemical Society. All rights reserved.

Influence of stoichiometry on dielectric properties of boundary layer ceramics based on yttrium-doped strontium titanate

Abstract Yttrium-doped (2%) SrTiO 3 -based ceramics with different ratios R=( Sr + Y )/ Ti (0.96⩽ R ⩽ 1.04) were prepared as sintered pellets in a reducing atmosphere. The pellets were then printed with an oxide mixture Bi 2 O 3 -PbO-B 2 O 3 and heated in air in order to produce boundary layer materials. The dielectric parameters were measured as functions of frequency and sample thickness. The influence of the ratio R on the properties is discussed.