scholarly journals SINTERING AND ELECTRICAL PROPERTIES IN AIR FOR A-SITE DEFICIENT (Sr0.7La0.3)1-yTiO3 PEROVSKITE SAMPLES WITH AND WITHOUT TiO2 PHASE

2012 ◽  
Vol 06 ◽  
pp. 1-6 ◽  
Author(s):  
MASASHI MORI ◽  
SHINTARO YABUI ◽  
YUTA HIGASHI ◽  
KEI-ICHIRO MURAI ◽  
TOSHIHIRO MORIGA
Keyword(s):  
Electrical Properties ◽  
Pore Formation ◽  
Perovskite Phase ◽  
Holding Time ◽  
Single Perovskite Phase ◽  
Sintering Characteristics ◽  
State Mixing ◽  
A Site ◽  
Tio2 Phase ◽  
Total Resistivity

The sintering and electrical properties of A-site-deficient perovskites, namely, ( Sr 0.7 La 0.3)0.85 TiO 3 with TiO 2 and ( Sr 0.7 La 0.3)0.88 TiO 3 with a single perovskite phase, were investigated in air using powders synthesized by solid-state mixing. ( Sr 0.7 La 0.3)0.85 TiO 3 showed much higher sintering characteristics than ( Sr 0.7 La 0.3)0.88 TiO 3. The relative density of ( Sr 0.7 La 0.3)0.85 TiO 3 reached 96% at 1500 °C with zero holding time, but decreased with increasing holding time, owing to pore formation inside the sample. The resistivity of ( Sr 0.7 La 0.3)0.85 TiO 3 was lower than that of ( Sr 0.7 La 0.3)0.88 TiO 3 at measurement temperatures ≤600 °C, although the reverse was observed at temperatures ≥700 °C. Because the total resistivity of ( Sr , La ) TiO 3 perovskites should be governed primarily by grain boundary resistivity at low temperatures, ( Sr 0.7 La 0.3)0.88 TiO 3 with many grain boundaries showed higher resistivity, compared to that of ( Sr 0.7 La 0.3)0.85 TiO 3.

Crystal Structure and Anomalous Sintering Behavior of (Sr0.7La0.3)1−xTiO3+δ Perovskites (0 ≤ x ≤ 0.12) Synthesized by the Pechini Method

2012 ◽  
Vol 9 (2) ◽  
Author(s):  
Masashi Mori ◽  
Kaoru Nakamura ◽  
Takanori Itoh
Keyword(s):  
Crystal Structure ◽  
Pore Formation ◽  
Perovskite Phase ◽  
Pechini Method ◽  
Phase Relationship ◽  
Sintering Behavior ◽  
Oxygen Release ◽  
Sintering Characteristics ◽  
Weight Decrease ◽  
A Site

The crystal structure, phase relationship and sintering characteristics of (Sr0.7La0.3)1−xTiO3+δ perovskites (0 ≤ x ≤ 0.12) have been studied using the Pechini method. High-temperature neutron diffraction analysis showed that (Sr0.7La0.3)TiO3+δ has an orthorhombic structure at room temperature and a cubic structure at 450 °C. (Sr0.7La0.3)0.88TiO3+δ showed a single perovskite phase and other samples with an A-site deficiency of 0 ≤ x ≤ 0.08 included secondary Ruddlesden-Popper phases. Sintering characteristics improved as the A-site deficiency increased and it was found that during sintering, (Sr0.7La0.3)0.88TiO3+δ expanded anomalously between 1400 °C and 1500 °C and for holding times between 0 h and 10 h at 1400 °C and 1500 °C. Additionally, observation of the samples by scanning electron microscopy showed that this expansion was caused by pore formation within the samples. All the samples showed a weight decrease at temperatures ≥1000 °C and the temperature at which oxygen release began rose as the A-site deficiency increased. The release of oxygen is likely to be related to pore formation.

Sintering Characteristics and Electrical Conductivity of (Sr1−xLax)TiO3 Synthesized by the Citric Acid Method

2011 ◽  
Vol 8 (5) ◽  
Author(s):  
Zhenwei Wang ◽  
Masashi Mori
Keyword(s):  
Electrical Conductivity ◽  
Citric Acid ◽  
Solid Oxide Fuel Cells ◽  
Perovskite Phase ◽  
Solid Oxide ◽  
Single Perovskite Phase ◽  
Reducing Atmosphere ◽  
Acid Method ◽  
Electrical Conductivities ◽  
Sintering Characteristics

The air-sintering characteristics and electrical conductivity of (Sr1−xLax)TiO3 perovskites (0 ≤ x ≤ 0.3) synthesized by the citric acid method were evaluated in terms of their use as interconnect materials in solid oxide fuel cells. A single perovskite phase of (Sr0.8La0.2)TiO3 powder was formed at 800 °C. In this powder, a Ruddlesden–Popper Sr2TiO4 layer appeared in the temperature range of 1100–1500 °C, and disappeared at 1600 °C. (Sr0.8La0.2)TiO3 powders which were calcined at 1000–1100 °C showed the best sintering characteristics. The relative density of the samples reached 94% at 1400 °C, although the Ruddlesden–Popper layer remained in this dense sample. Electrical conductivities of (Sr1−xLax)TiO3 bars at 1000 °C were approximately 0.10–1.1 S cm−1 in air and 7.1–12 S cm−1 in a reducing atmosphere. For a (Sr0.9La0.1)TiO3 pellet placed between both air and reducing atmospheres, the conductivity at 850 °C was 0.033 S cm−1, which is close to that in air. No compositional dependency on electrical conductivity was observed for the (Sr1−xLax)TiO3 pellets.

A-Site and B-Site Non-stoichiometry and Sintering Characteristics of (Sr1−xLax)1−yTi1−zO3 Perovskites

2011 ◽  
Vol 8 (5) ◽  
Author(s):  
Masashi Mori ◽  
Zhenwei Wang ◽  
Takanori Itoh ◽  
Shintarou Yabui ◽  
Kei-ichiro Murai ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Solid State ◽  
Charge Compensation ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Sintering Characteristics ◽  
State Mixing ◽  
A Site ◽  
La Doped ◽  
Cell Volumes

The A-Site and B-Site non-stoichiometry and sintering characteristics of (Sr1−xLax)1−yTi1−zO3 perovskites were studied using samples prepared by solid-state mixing. A-Site or B-Site deficiency was observed for La-doped SrTiO3 perovskites, and this increased with increasing La content. For A-Site deficient (Sr1−xLax)1−yTiO3 perovskites, the cell volumes decreased although the reverse was observed for B-Site deficient (Sr1−xLax)Ti1−zO3 perovskites. This may be related to number of B-Site vacancies in the perovskites through charge compensation. It was found that A-Site and B-Site deficiencies increase the density of (Sr1−xLax)1−yTi1−zO3 perovskites. These characteristics may prove useful in the development of solid oxide fuel cell interconnect materials.

scholarly journals Effects of A-site nonstoichiometry on oxide ion conduction in 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 ceramics

2016 ◽  
Vol 06 (02) ◽  
pp. 1650012 ◽  
Author(s):  
Sasiporn Prasertpalichat ◽  
Whitney Schmidt ◽  
David P. Cann
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Perovskite Phase ◽  
Ion Conduction ◽  
Homogeneous Microstructure ◽  
Cubic Symmetry ◽  
A Site ◽  
Oxide Ion Conduction ◽  
Oxide Ion

Lead free 0.94(Bi[Formula: see text]Na[Formula: see text]TiO3–0.06BaTiO3 ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping (through Bi-excess) and acceptor-doping (through Na-excess). Both stoichiometric and nonstoichiometric ceramics exhibited a single perovskite phase with pseudo-cubic symmetry. A significant improvement in the dielectric properties was observed in Bi-excess compositions and a deterioration in the dielectric properties was observed in Na-excess compositions. Impedance spectroscopy was utilized to analyze the effects of A-site nonstoichiometry on conduction mechanisms. Compositions with Bi-excess resulted in an electrically homogeneous microstructure with an increase in resistivity by [Formula: see text]3–4 orders of magnitude and an associated activation energy of 1.57[Formula: see text]eV which was close to half of the optical bandgap. In contrast, an electrically heterogeneous microstructure was observed in both the stoichiometric and Na-excess compositions. In addition, the Na-excess compositions exhibited low resistivities ([Formula: see text]-cm) with characteristic peaks in the impedance data comparable to the recent observations of oxide ion conduction in (Bi[Formula: see text]Na[Formula: see text]TiO3. Long term annealing studies were also conducted at 800[Formula: see text]C to identify changes in crystal structure and electrical properties. The results of this study demonstrates that the dielectric and electrical properties of 0.94(Bi[Formula: see text]Na[Formula: see text]TiO3–0.06BaTiO3 ceramics are very sensitive to Bi/Na stoichiometry.

Influence of Cr deficiency on sintering, thermal expansion and electrical properties of La0.75Sr0.25Cr1−xO3−δ as a SOFC interconnect material

2016 ◽  
Vol 30 (11) ◽  
pp. 1650127 ◽  
Author(s):  
Yi Ren ◽  
Wen Ma ◽  
Xiaoying Li ◽  
Jun Wang ◽  
Yu Bai ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Electrical Properties ◽  
Perovskite Phase ◽  
Ignition Process ◽  
Thermal Expansion Coefficients ◽  
Auto Ignition ◽  
Pure Perovskite Phase ◽  
Maximum Conductivity ◽  
Expansion Coefficients ◽  
Interconnect Material

The SOFC interconnect materials La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] [Formula: see text]–[Formula: see text] were prepared using an auto-ignition process. The influences of Cr deficiency on their sintering, thermal expansion and electrical properties were investigated. All the samples were pure perovskite phase after sintering at 1400[Formula: see text]C for 4 h. The cell volume of La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] decreased with increasing Cr deficient content. The relative density of the sintered bulk samples increased from 93.2% [Formula: see text] to a maximum value of 94.7% [Formula: see text] and then decreased to 87.7% [Formula: see text]. The thermal expansion coefficients of the sintered bulk samples were in the range of [Formula: see text]–[Formula: see text] (30–1000[Formula: see text]C), which are compatible with that of YSZ. Among the investigated samples, the sample with 0.02 Cr deficiency had a maximum conductivity of 40.4 Scm[Formula: see text] and the lowest Seebeck coefficient of 154.8 [Formula: see text]VK[Formula: see text] at 850[Formula: see text]C in pure He. The experimental results indicate that La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] has the best properties and is much suitable for SOFC interconnect material application.

Effect of Sintering Temperature on Electrical Properties of SFN Ceramics Doped with Al Prepared by a Solid-State Reaction Technique

2016 ◽  
Vol 675-676 ◽  
pp. 527-530
Author(s):  
Thanatep Phatungthane ◽  
Kachaporn Sanjoom ◽  
Denis Russell Sweatman ◽  
Buagun Samran ◽  
Chamnan Randorn ◽  
...  
Keyword(s):  
Solid State ◽  
Electrical Properties ◽  
Solid State Reaction ◽  
Sintering Temperature ◽  
Perovskite Phase ◽  
Dielectric Behavior ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Solid State Reaction Technique ◽  
Pure Perovskite Phase

In the present work, strontium iron niobate SrFe0.5Nb0.5O3 ceramics doped with aluminum were synthesized by a solid-state reaction technique. Phase formation investigation by X-ray diffraction technique (XRD) revealed that all ceramics exhibited pure perovskite phase with orthorhombic symmetry. Grain size observed by electron microscopy (SEM) was found to increase with increasing sintering temperature. The electrical properties and related parameters of the ceramics were also measured. The ceramics exhibit very good dielectric behavior and have a significant potential for dielectric applications.

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