Hydrothermal Synthesis, Characterization, and Sintering Behavior of Core-Shell Particles: A Principle Study on Lanthanum Strontium Cobaltite Coated with Nanosized Gadolinium Doped Ceria

Abstract

In this work, nanostructured (La 0.6 Sr 0.4 ) 0.99 CoO 3 (LSC)-Ce 0.8 Gd 0.2 O 1.9 (CGO) core-shell particles were prepared by precipitating CGO nanoparticles on the surface of LSC particles under hydrothermal conditions. The as-prepared core-shell particles were sintered by spark plasma sintering (SPS) and conventional sintering, and the microstructure evolution and densification behavior were studied. Dense microstructures were reached using both sintering methods at relatively low temperatures. In the case of SPS, the core-shell architecture was partially maintained and nano-structured CGO grains were formed, while conventional sintering led to the formation of larger CGO grains. This work covers a detailed characterization of (a) the individual LSC-CGO core-shell particles and (b) the composites after densification.Ceramics 2018, 1 247 production. However, obtaining such desired structures in a dense bulk form is challenging due to the fact that the sintering temperatures for these two materials are different and that the high temperature required for densifying a CGO of poor sinterability (1400-1600 • C to reach the full density of pure CGO) is problematic [7,8]. Moreover, since LSC and CGO have rather different thermal expansion coefficients, it is even more difficult to obtain a fully dense large sample without cracking [9]. Ideally, for OTM applications, the microstructure after sintering should consist of small, but still percolating, grain networks in order to maintain both the ionic and electronic percolations. Therefore, it requires fine control on the phase volume fractions and phase arrangement in the primary powders. Such a microstructure is difficult to obtain with conventional sintering, at high temperatures, due to the severe structural rearrangements [10,11].One possible way to realize a controlled and designed microstructure in a densified composite is to use core-shell nanostructures with a pre-arranged architecture as building blocks for bottom-up manufacturing of functional nanocomposite ceramics. Recent examples realizing this concept include the use of PbTe-PbS core-shell particles as building blocks for highly homogeneous thermoelectrics [12], ceramics with excellent dielectric properties made from core-shell structured SiO 2 -TiO 2 particles synthesized using a solvothermal route [13], and the application of SrTiO 3 -NiFe 2 O 4 core-shell particles prepared using a combination of sol-gel and co-precipitation methods to obtain structured ceramics [14].However, the densification of the core-shell particles to a ceramic without destroying the original structure by using the conventional sintering is challenging because of the inherent severe structural rearrangement. Even designed core-shell structures do not necessarily lead to core-shell ceramic composites, due to a lattice mismatch, a sinterability difference, interfacial diffusions and/or phase reactions. An interesting alternative to the conventional sintering is spark plasma sintering (SPS), which combines a pulsed direct electric cu...

Influence of Te-Incorporated LaCoO3 on Structural, Morphology and Magnetic Properties for Multifunctional Device Applications

“…Microwave heating, chemical co-precipitation, sol–gel auto-combustion [ 22 ], micro- and nano-emulsions, hydrothermal techniques, high-temperature breakdown, and reverse micelle have all been used to create cobaltite magnetic nanoparticles (NPs) [ 23 , 24 , 25 ]. The best way to produce LaCoO 3 is through hydrothermal synthesis because it is easy, cheap, and safe for the environment.…”

Influence of Te Incorporated LaCoO3 on Structural, Morphology and Magnetic Properties

“…Microwave heating, chemical co-precipitation, sol-gel auto-combustion [22], microand nano-emulsions, hydrothermal techniques, high-temperature breakdown, and reverse micelle have all been used to create cobaltite magnetic nanoparticles (NPs) [23][24][25]. The best way to produce LaCoO 3 is through hydrothermal synthesis because it is easy, cheap, and safe for the environment.…”

The Effect of TiC Additive on Mechanical and Electrical Properties of Al2O3 Ceramic

“…Therefore, to decrease the sintering temperature spark plasma sintering (SPS) was used as an alternative consolidation method. Using this novel technology facilitates fast consolidation, allows fabrication of fully dense composites and avoids grain growth [35][36][37][38][39][40].…”