Hydrothermal synthesis, sintering behavior and oxide ionic conductivity of Na-doped lanthanum silicate

Abstract Li1.5Al0.5Ti1.5(PO4)3 (LATP) powders were prepared from different NO x -free precursors using an aqueous-based solution-assisted solid-state reaction (SA-SSR). The sintering behavior, phase formation, microstructure and ionic conductivity of the powders were explored as a function of sintering temperature. The powders showed a relatively narrow temperature windows in which shrinkage occurred. Relative densities of 95% were reached upon heating between 900 and 960 °C. Depending on the morphological features of the primary particles, either homogeneous and intact microstructures with fine grains of about <2 µm in size or a broad grain size distribution, micro-cracks and grain cleavages were obtained, indicating the instability of the microstructure. Consequently, the ceramics with a homogeneous microstructure possessed a maximum total ionic conductivity of 0.67 mS cm−1, whereas other ceramics reached only 0.58 mS cm−1 and 0.21 mS cm−1.

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Sintering Behavior and Mechanical Properties of Mullite Fibers/Hydroxyapatite Ceramic

Materials ◽

10.3390/ma11101859 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1859 ◽

Cited By ~ 3

Author(s):

Xueni Zhao ◽

Qingyao Liu ◽

Jianjun Yang ◽

Weigang Zhang ◽

Yao Wang

Keyword(s):

Mechanical Properties ◽

Hydrothermal Synthesis ◽

Bending Strength ◽

Fiber Content ◽

Silicate Glasses ◽

Sintering Behavior ◽

Composite Powders ◽

Hydroxyapatite Ceramic ◽

Dense Microstructure ◽

Mullite Fibers

The effect of fiber content and sintering temperature on sintering behavior and mechanical properties of mullite fibers/hydroxyapatite composites was studied. The composites were fabricated by hydrothermal synthesis and pressureless sintering. The amount of fibers was varied from 5 wt % to 15 wt % through hydrothermal synthesis, mullite fibers and hydroxyapatite composite powders were subsequently sintered at temperatures of 1150, 1250, and 1350 °C. The composites presented a more perturbed structure by increasing fiber content. Moreover, the composites experienced pore coalescence and exhibited a dense microstructure at elevated temperature. X-ray diffraction indicated that the composites underwent various chemical reactions and generated silicate glasses. The generation of silicate glasses increased the driving force of particle rearrangement and decreased the number of pores, which promoted densification of the composites. Densification typically leads to increased hardness and bending strength. The study proposes a densification mechanism and opens new insights into the sintering properties of these materials.

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Low-Temperature Prepared Multi-Elements Doped CeO2 Electrolyte

ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology ◽

10.1115/fuelcell2009-85221 ◽

2009 ◽

Author(s):

Horng-Yi Chang ◽

Yao-Ming Wang

Keyword(s):

Ionic Conductivity ◽

Low Temperature ◽

Mixed Oxide ◽

Sintering Temperature ◽

Solid Oxide ◽

Evaporation Method ◽

Pure Phase ◽

Doped Ceo2 ◽

Oxide Ionic Conductivity ◽

Homogeneous Composition

CeO2 materials doped with the di- or tri-valent metals possess high oxide ionic conductivity at low temperature for potential electrolyte use in intermediate temperature solid oxide fuel cell (SOFC). However, multi-elements doped CeO2-based electrolyte, (La1-x-ySrxBay)0.175Ce0.825O2-δ (LSBC) in this work, with pure phase is difficultly synthesized at low calcination temperature. High sintering temperature, e.g. > 1500°C, is also needed in conventional mixed oxide method. In this work, nanoparticles less than 50nm of LSBC can be prepared by solution-evaporation method at constant temperature. Pure fluorite crystal structure can be obtained lower than 700°C. The optimal mole ratio of LSBC/citric acid in prepared solution is 1/2 to achieve homogeneous composition and pure phase of LSBC. Small grain size of about 1μm average is observed for 1300°C-microwave sintered LSBC by solution-evaporation method. The ionic conductivity of 1400°C-conventional sintered and 1300°C-microwave sintered LSBC prepared by solution-evaporation method is about 0.006 S/cm at 600°C but less than 0.004 S/cm at 600°C even for 1500°C-conventional sintered LSBC prepared by mixed oxide method.

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