Versatile Molten Salt Synthesis of Manganite Perovskite Oxide Nanocrystals and Their Magnetic Properties

Abstract

Manganite perovskite oxides exhibit a wide range of properties relevant for catalysis, energy conversion and spintronics. Such behaviors can be deeply modified at the nanoscale where confinement and surface effects may prevail. Interesting properties could then emerge from manganite perovskite nanocrystals, although their synthesis remains a challenge. The present study reports a versatile synthesis of manganite perovskite nanocrystals by using molten salts as high temperature liquids in the 600–750 °C range. Through X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning and transmission electron microscopies, we show that many substitutions on the A perovskite site are within reach by applying the approach to La2/3Sr1/3MnO3, La2/3Ca1/3MnO3 and La1/3Pr1/3Ca1/3MnO3 cubic‐shape nanocrystals with diameter of 20, 22 and 38 nm, respectively. The magnetic properties of these nanocrystals are then investigated at 5 K, highlighting the coexistence of a ferromagnetic phase typical of the bulk, with disordered and non‐magnetic domains, which presumably arise from the nanoscale and surface effects.

Structure–Activity Relationship in Manganese Perovskite Oxide Nanocrystals from Molten Salts for Efficient Oxygen Reduction Reaction Electrocatalysis

“…Indeed, we have previously shown that Mn is reduced within a 1 nm thick layer at the surface of pc-LSMO nanocubes because of oxygen vacancies, 21,33 yielding a surface Mn oxidation state close to 3.3. 33 Likewise, X-ray photoelectron spectroscopy (XPS, Figure S16) yields a surface Mn oxidation state of 3.2 for l-LSMO. Given the precision of XPS (±0.1 on the oxidation state), pc-LSMO and l-LSMO possess identical surface oxidation states.…”

“…This apparent discrepancy may originate first from a change in the oxidation state of Mn at the surface of the particles. Indeed, we have previously shown that Mn is reduced within a 1 nm thick layer at the surface of pc-LSMO nanocubes because of oxygen vacancies, 21,33 yielding a surface Mn oxidation state close to 3.3. 33 Likewise, X-ray photoelectron spectroscopy (XPS, Figure S16) yields a surface Mn oxidation state of 3.2 for l-LSMO.…”

Recent Developments on Molten Salt Synthesis of Inorganic Nanomaterials: A Review

“…On a similar line, Wu et al mentioned several perovskite nanocrystals synthesized by the MSS in their review . Gonell et al reported the synthesis of various magnetite perovskite nanocrystals using the MSS . There was a separate article on the TMSS of functional perovskite published by Li et al One specific review was published on the synthesis of BaTiO 3 NPs using several techniques including the MSS .…”

“…176 Gonell et al reported the synthesis of various magnetite perovskite nanocrystals using the MSS. 177 There was a separate article on the TMSS of functional perovskite published by Li et al 62 One specific review was published on the synthesis of BaTiO 3 NPs using several techniques including the MSS. 178 We have tabulated various perovskite nanomaterials synthesized by the MSS along with the salt used, MOT, and particle characteristics in Table S4.…”

Experimental Descriptors for the Synthesis of Multicationic Nickel Perovskite Nanoparticles for Oxygen Reduction

“…The synthesis of LaNiO 3 and La 2 NiO 4 was performed using metal nitrates (La­(III) and Ni­(II)) of varying ratios. KNO 3 was used as solvent to dissolve metal nitrates and to efficiently supply oxygen for the synthesis of perovskites. , The powder X-ray diffraction (XRD) patterns for the LaNiO 3 system (Figure S1) indicate that high temperature (800 °C) treatments and long reaction times (6 h) are needed to obtain pure LaNiO 3 . When the ratio of La and Ni reagents is adjusted to target La 2 NiO 4 , even prolonged heating at 800 °C for 14 h yields LaNiO 3 as the major product with a small amount of La 2 NiO 4 (Figure S2).…”