R. Morineau

Bio: R. Morineau is an academic researcher. The author has contributed to research in topics: Conductivity & Perovskite (structure). The author has an hindex of 2, co-authored 3 publications receiving 46 citations.

Comparison of different synthesis methods for nasicon ceramics

Abstract: Various methods for the synthesis of Na2Zr2P2SiO12 ceramics have been investigated. The methods differ by the order of mixing and the use of acetylacetone to decrease the reactivity of zirconium. The homogeneity of the powders prior to calcination has been checked by 31P NMR. Their reactivity towards crystallization is not drastically different. The sintering behaviour is much better in powders in which the zirconium reactivity has been decreased. The effect of the processing on the resulting ionic conductivity of the ceramics has been studied.

Synthesis of Superconducting Perovskite by Coprecipitation of Hydroxides

Abstract: The synthesis of the superconducting perovskite YBa2Cu3O7 using hydroxides as starting precursors has been investigated. Hydroxides are homogeneously coprecipitated from mixed alcohol-water solutions without loss of barium. Upon heat-treatment the perovskite phase rapidly forms around 750°C. However, it remains tetragonal even after long time annealing in oxygen ambient. This is related to an unusual microtwinning in the (ac) plane.

Scandium-Substituted Na3Zr2(SiO4)2(PO4) Prepared by a Solution-Assisted Solid-State Reaction Method as Sodium-Ion Conductors

Abstract: As possible electrolyte materials for all-solid-state Na-ion batteries (NIBs), scandium-substituted Na3Zr2(SiO4)2(PO4) in the structure of NASICONs (Na superionic conductors) has received hardly any attention so far, although among all the trivalent cations, Sc3+ might be the most suitable substitution ion for Na3Zr2(SiO4)2(PO4) because the ionic radius of Sc3+ (74.5 pm) is the closest to that of Zr4+ (72.0 pm). In this study, a solution-assisted solid-state reaction (SASSR) method is described, and a series of scandium-substituted Na3Zr2(SiO4)2(PO4) with the formula of Na3+xScxZr2-x(SiO4)2(PO4) (NSZSPx, 0 ≤ x ≤ 0.6) have been prepared. This synthesis route can be applied for powder preparation on a large scale and at low cost. With increasing degrees of scandium substitution, the total conductivity of the samples also increases. An optimum total Na-ion conductivity of 4.0 × 10–3 S cm–1 at 25 °C is achieved by Na3.4Sc0.4Zr1.6(SiO4)2(PO4) (NSZSP0.4), which is the best value of all reported polycrystalline ...

Sodium Ion Diffusion in Nasicon (Na3Zr2Si2PO12) Solid Electrolytes: Effects of Excess Sodium

Abstract: The Na superionic conductor (aka Nasicon, Na1+xZr2SixP3–xO12, where 0 ≤ x ≤ 3) is one of the promising solid electrolyte materials used in advanced molten Na-based secondary batteries that typically operate at high temperature (over ∼270 °C). Nasicon provides a 3D diffusion network allowing the transport of the active Na-ion species (i.e., ionic conductor) while blocking the conduction of electrons (i.e., electronic insulator) between the anode and cathode compartments of cells. In this work, the standard Nasicon (Na3Zr2Si2PO12, bare sample) and 10 at% Na-excess Nasicon (Na3.3Zr2Si2PO12, Na-excess sample) solid electrolytes were synthesized using a solid-state sintering technique to elucidate the Na diffusion mechanism (i.e., grain diffusion or grain boundary diffusion) and the impacts of adding excess Na at relatively low and high temperatures. The structural, thermal, and ionic transport characterizations were conducted using various experimental tools including X-ray diffraction (XRD), differential sca...

Room temperature demonstration of a sodium superionic conductor with grain conductivity in excess of 0.01 S cm−1 and its primary applications in symmetric battery cells

Abstract: The lack of suitable candidate electrolyte materials for practical application limits the development of all-solid-state Na-ion batteries. Na3+xZr2Si2+xP1−xO12 was the very first series of NASICONs discovered some 40 years ago; however, separation of bulk conductivity from total conductivity at room temperature is still problematic. It has been suggested that the effective Na-ion conductivity is ∼10−4 S cm−1 at room temperature for Na3+xZr2Si2+xP1−xO12 ceramics; however using a solution-assisted solid-state reaction for preparation of Na3+xZr2Si2+xP1−xO12, a total conductivity of 5 × 10−3 S cm−1 was achieved for Na3.4Zr2Si2.4P0.6O12 at 25 °C, higher than the values previously reported for polycrystalline Na-ion conductors. A bulk conductivity of 1.5 × 10−2 S cm−1 was revealed by high frequency impedance spectroscopy (up to 3 GHz) and verified by low temperature impedance spectroscopy (down to −100 °C) for Na3.4Zr2Si2.4P0.6O12 at 25 °C, indicating further the potential of increasing the related total conductivity. A Na/Na3.4Zr2Si2.4P0.6O12/Na symmetric cell showed low interface resistance and high cycling stability at room temperature. A full-ceramic cell was fabricated and tested at 28 °C with good cycling performance.

Improving the ionic conductivity of NASICON through aliovalent cation substitution of Na3Zr2Si2PO12

Abstract: Doping the zirconium site in NASICON (Na3Zr2Si2PO12) with lower valent cations enhanced the ionic transport of the material. Both Na3.2Zr1.8M0.2Si2PO12 (M=Al3+, Fe3+, Y3+) and Na3.4Zr1.8M0.2Si2PO12 (M=Co2+, Ni2+, Zn2+) exhibited a higher bulk conductivity than undoped Na3Zr2Si2PO12 at room temperature. A decrease in the low temperature activation energy for all doped NASICON was observed, which helped contribute to the higher room temperature conductivity. The lower activation energy and enhanced conductivity of doped materials were a result of alterations in the NASICON structure. The charge imbalance created by aliovalent substitution increased the sodium in the lattice resulting in more charge carriers with better mobility. Furthermore, the conductivity was optimized by the ionic radius of the species in the zirconium site. Ultimately, NASICON doped with a +2 oxidation state cation having an ionic radius of approximately 0.73 A (Zn and Co) attained a maximum in conductivity. Zn-doped NASICON displayed the greatest room temperature bulk conductivity of 3.75 × 10−3 S/cm, while Co-doped NASICON demonstrated the greatest total conductivity of 1.55 × 10−3 S/cm.