Molten Salt Synthesis Method Research Articles

Molten salt synthesis of Ti-Si-C coating on SiC particles and hot pressing of the prepared powders

SiC particles coated with Ti-Si-C layer were prepared by the molten salt synthesis method using NaCl-KCl eutectic mixture as the reaction medium and Ti metal powder as the Ti source. The synthesis was conducted under static argon atmosphere at 900 °C for 1–3 h. The post-synthesis treatment included dissolution of salts in hot water, followed by ultrasonic dispersion and sedimentation procedures. The thickness of the Ti-Si-C layer varied from 0.1 to 0.9 μm as the ratio of Ti to SiC components in the starting mixture changed from 0.05 to 0.4. The layer contained mainly nanocrystalline Ti5Si3, minor phases were TiC and Ti3SiC2. The as-prepared powders were hot pressed under 30 MPa at 1700 °C. The densification behavior of the samples during hot pressing as well as changes both in phase composition and in microstructure were studied. The flexural strength of the hot-pressed samples increased with an increase in the Ti:SiC molar ratio, giving the value as high as 213 ± 20 MPa for the sample with Ti/SiC = 0.4.

Review on preparation technology of carbide resistant ultra-high temperature ceramic fiber

The rapid development of hyper-sonic vehicles has put forward an urgent demand for ultra-high temperature resistance ceramic fibers ceramic matrix composites. The properties of ultrahigh-temperature ceramic matrix composites made of carbon-based ultra-high temperature resistance ceramic fibers are excellent. Therefore, the preparation processes of several commonly used carbide-resistant ultrahigh-temperature ceramic fibers are described in detail. This review compares the advantages and disadvantages of five common methods (Molten-salt synthesis method, Chemical Vapor Reaction Method, Chemical Vapor Deposited method, Sol-Gel Method & Polymer-Derived method) for preparing ceramic fibers, summarizes the preparation methods that should be used in the face of different preparation requirements, and evaluates the improvement and prospect of each method. Among them, the polymer-derived method, as the most difficult and effective preparation method, has been given great hope by material scientists.

Band engineering of single-halogen layered Sillén oxyhalide, BaBiO2X (X = Cl, Br, and I): The role of lone-pair effect in photocatalysts

Band structure engineering is an effective way to improve the performance of photocatalysis. Herein, layered oxyhalides, BaBiO2X (X = Cl, Br, and I), with single halogen layers were synthesized by using molten salt synthesis method. Density functional theory (DFT) calculation reveals that the valance band maximum (VBM) of BaBiO2X mainly consists of O 2p orbitals, not halogen p orbitals (Cl-3p, Br-4p, and I-5p), which means that this X1 oxyhalide owns the stability against self-degradation by photogenerated holes during the photocatalytic process. Simultaneously, with the increasing of atomic number from BaBiO2Cl to BaBiO2I, the band gap (Eg) decreases from 3.523 eV to 2.777 eV. Eventually, BaBiO2I exhibits the highest photocatalytic RhB degradation performance among all samples, mostly owning to the enhanced light absorption and improved separation and migration efficiency of photogenerated carriers. This study provides a new idea for designing bismuth-based photocatalysts by band engineering to solve environmental pollution.

CaH2-Assisted Molten Salt Synthesis of Zinc-Rich Intermetallic Compounds of RhZn13 and Pt3Zn10 for Catalytic Selective Hydrogenation Application

Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH2-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn13 and Pt3Zn10 in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn13 and Pt3Zn10 catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn13 and Pt3Zn10 could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn.

Molten Salt Synthesized CaTa4O11:Er3+/Yb3+ with Superior Upconversion Luminescence.

Low phonon tantalate-based phosphors with a layer structure are considered to have excellent upconversion luminescence (UCL) intensity, which could be reduced due to the existence of impure phase defects and inappropriate doped rare earth ions. To improve their UCL performance, we have prepared single-phase CaTa4O11:Er3+/Yb3+ samples by a molten salt synthesis (MSS) using KCl as the reaction medium and compared its UCL properties with counterparts made by a conventional solid-state reaction (SSR) in this study. We have demonstrated that the MSS samples have a much higher UCL intensity under 980 nm laser excitation than the SSR ones due to accurate replacement of Ca2+ sites by Er3+/Yb3+ in high-purity single-phase MSS samples. We have further enhanced the green UCL intensity of the MSS samples by 1.57 times via acid picking (AP). Under 980 nm laser excitation at a high powder density of 61.3 W/cm2, the green UCL intensity of the MSS-AP samples can reach 3.72 times that of the SSR-AP samples. For potential luminescence thermometry applications, the maximum absolute sensitivity (SA) of the MSS-AP samples reaches 0.01316 K-1 at 501 K based on the luminescence intensity ratio. This study shows that CaTa4O11:Er3+/Yb3+ phosphors prepared by the MSS method are single-phase samples with excellent pure green UCL as a suitable temperature sensing material.

New insights into the synthesis of Sillén–Aurivillius oxyhalides: molten salts induce interlayer halogen competing reaction

The molten-salt synthesis method offers a special liquid reaction environment that expedites the diffusion of reactive elements and provides the competing reaction of the migrated halogen atoms during the synthesis of Sillén–Aurivillius oxyhalides.

Development of barium hexaferrite core–shell composites as high-performance microwave absorption by optimizing hydrothermal synthesis

In conjunction with the enhancement of societal living standards and the rapid development of information technology, an extensive variety of high-capacity electronic devices are being introduced to the market. The heightened demands result in the generation of electromagnetic wave radiation, which poses a potential risk to human well-being. Barium hexaferrite (BHF) is one of the radar-absorbing materials (RAMs) that can absorb electromagnetic waves because it has a high anisotropic field. However, its drawbacks are narrow absorption and less stability. Molybdenum disulfide (MoS2), is the best candidate for the reinforcement of BHF. The study investigated the impact of increasing the thiourea, temperature, hydrothermal holding time, and sample thickness on reflection loss. This study used a two-step molten salt and hydrothermal synthesis to make a BaFe12O19@MoS2 core-cell composite. Two-step molten salt and hydrothermal synthesis methods created single-phase BaFe12O19@MoS2 core-cell composites that worked well. The results showed that adding MoS2 to BHF changed BHF's magnetic properties from hard to soft. Increasing the hydrothermal temperature up to 220 °C effectively reduced the reflection loss of BaFe12O19@MoS2. On a 2 mm thick sample containing 100 mmol thiourea, the study achieved an electromagnetic wave absorption of 99.97 % with a reflection loss of –35.41 dB (17.37 GHz). The results of this research can be applied to protect electronic devices vulnerable to signal interference from satellite radar systems at frequencies of 12–18 GHz

120 nm wide band tunable pulsed laser generation employing vanadium carbide MXene/polyvinyl alcohol (V2C-PVA) film

MXene, a group of 2D materials, has garnered significant attention from researchers due to its impressive characteristics, such as large surface area, high metallic conductivity, and strong nonlinear saturable absorption. These properties make MXene an excellent material for exploring new possibilities in ultrafast photonics technology. The present study has demonstrated that vanadium carbide (V2C) MXene can function as a saturable absorber (SA) and effectively generate Q-switching pulses in the 1.9 μm wavelength region. The molten salt synthesis method was used to synthesize V2C MXene, which involved the selective etching of aluminum (Al) layers from the V2AlC MAX Phase precursor. The V2C MXene was transformed into a thin film by mixing it with polyvinyl alcohol (PVA) using a solution casting technique. The resulting V2C-PVA film was found to have saturable absorption properties, with a modulation depth of 8% and saturation intensity of 1.6 MW cm −2. Upon integrating the V2C-PVA film into the Thulium/Holmium-doped fiber laser (THDFL) cavity, stable Q-switching pulses were realized at a central wavelength of 1896.9 nm with 13.9 nm of 3-dB spectral bandwidth. At the maximum pump power of 448.7 mW, the 2.2 μs of pulse duration, 58.26 kHz of repetition rate, and 31 nJ of pulse energy were achieved. By adjusting the tunable bandpass filter (TBPF) integrated within the THDFL cavity, the system has a tunable spectral range of approximately 120.75 nm, from 1889.75 nm to 2010.5 nm. The exceptional performance of V2C-based SA for Q-switching operation showcases the immense potential of other MXene materials in the future of photonics applications.

Molten salt synthesis of highly crystalized (TaNbTiV)C flake and its electromagnetic wave absorption property

M site high-entropy transition metal carbide powder, (TaNbTiV)C, is synthesized via a molten salt synthesis method. Corresponding metal oxides and graphite are used as starting materials, with CaCl2 serving as the reaction medium. XRD and SEM techniques are employed to observe the phase transition and morphology of the reaction product at elevated temperatures. Pure (TaNbTiV)C powder is obtained at 1500 °C, exhibiting highly crystallized flake-like morphology and even distribution of micro-scale elements. The electromagnetic wave (EMW) absorption performance of (TaNbTiV)C in the frequency range of 1–18 GHz is studied by fabricating (TaNbTiV)C/paraffin wax with 10–50 vol % absorbent contents. Paraffin-based sample with 50 vol% content of (TaNbTiV)C exhibits the lowest reflection loss (−37.1 dB) and an effective absorption bandwidth (EAB) of 4.6 GHz. Conductive and dielectric losses are identified as its main mechanisms for EM wave absorption, while magnetic loss does not significantly affect its EM wave absorption ability. The significance of this work lies in the detailed elucidation of the fabrication and purification process involved in molten salt synthesis of flake-like (TaNbTiV)C, as well as the clarification of its electromagnetic wave absorbing mechanism.

BaAl<sub>1.4</sub>Si<sub>0.6</sub>O<sub>3.4</sub>N<sub>0.6</sub>:Eu<sup>2+</sup> green phosphors’ application for improving luminous performance

The molten salt synthesis (MSS) method was used to effectively prepare green phosphors BaAl<sub>1.4</sub>Si<sub>0.6</sub>O<sub>3.4</sub>N<sub>0.6</sub>:Eu<sup>2+</sup> (or BSON:Eu<sup>2+</sup>) via one homogeneous sphere-like morphology utilizing NaNO3 in the form of the reacting agent. The phosphors produced one wide stimulation spectrum between 250 and 460 nm, as well as a significant green emission has a maximum point at 510 nm owing to the 4f<sup>6</sup>5d<sup>1</sup>-4f<sup>7</sup> (<sup>8</sup>S<sub>7/2</sub>) shifts for Eu<sup>2+</sup> ions. With illumination under 365 as well as 450 nm, the ideal discharge strengths for the specimen prepared utilizing melted salt would receive a boost of 17% and 13%, surpassing the specimen prepared utilizing the traditional solid-state reaction (SSR) approach. The abatement of concentration for the ions of Eu<sup>2+</sup> from BSON:Eu<sup>2+</sup> is 5 mol%. In addition, the interactivity of dipole-dipole would be the cause of said abatement. Heat abatement would be studied utilizing the formation coordinate method with abatement temperature reaching ∼200 <sup>o</sup>C. Elemental mapping as well as power-dispersing X-ray spectroscopy (EDS) spectra demonstrated that the expected BaAl<sub>1.4</sub>Si<sub>0.6</sub>O<sub>3.4</sub>N<sub>0.6</sub>:Eu<sup>2+</sup> materials were formed.

Fabrication of grain-oriented PbNb2O6-based high temperature piezoelectric ceramics

Grain-oriented Sr and Ti modified lead metaniobate (Pb0.96Sr0.04)Nb1.96Ti0.05O6 (PSNT) ceramics with 4 mol% excess of Nb2O5 were prepared by templated grain growth method. The needle-like PSNT templates were obtained through the molten salt synthesis method. The effects of the template concentration (5, 10, 20 and 30 wt%) on the texture degree, microstructure, and electrical properties of textured ceramics were investigated. Improved electromechanical properties were found along the direction perpendicular to the sheet in textured PSNT ceramics, which shows the preferential orientation. An excess of templates would seriously deteriorate the properties of textured ceramics. The textured PSNT ceramics with 5 wt% templates exhibit high Curie temperature Tc of 545 °C, and improvement in piezoelectric coefficient d33 by 9% (d33 = 98 pC/N) and g33 by 45% (g33 = 42 × 10−3 Vm/N), as well as electromechanical coupling coefficient k31 by 18% (k31 = 0.26) compared to randomly oriented ceramics. The study demonstrates that grain-orientation controlling in PN-based ceramics is a potential way to improve the piezoelectric properties while maintaining high Curie temperature.

Achieving perfect white light, color tunability and X-ray scintillation in nanocrystalline La2Hf2O7:Eu3+,Bi3+ by photon energy and doping engineering

Materials which can demonstrate multifunctional lighting efficacy could be boon towards sustainable and developed economy owing to large materials crunch and huge electricity demands. In this work, we have hit three birds with one stone by judicious choice of photon energy and dopant composition engineering in bismuth sensitized Eu3+-doped La2Hf2O7 nanoparticles prepared by a molten salt synthesis method. Bismuth is found to stabilized at both La3+ and Hf4+ sites with Bi@La get excited at high photon energy whereas both Bi@La and Bi@Hf get co-excited at low photon energy to produce perfect amalgam of blue and green Bi3+ emissions upon excitation at 365 nm which couples with Eu3+ red emission and produces white light with (0.31, 0.32) color coordinate. Also, color tunability from violet-blue-purple-pink to orangish red is successfully achieved by efficient Bi3+ → Eu3+ energy transfers via electric multipolar interaction. Density functional theory (DFT) calculations for defect formation energy and density of state (DOS) supported distribution of Bi3+ at both La3+ and Hf4+ sites as well as high feasibility of Bi3+ → Eu3+ energy transfers. Moreover, the La2Hf2O7:0.5%Bi3+,x%Eu3+ NPs demonstrated excellent Eu2+/Eu3+ radioluminescence properties. These characteristics of the La2Hf2O7:0.5%Bi3+,x%Eu3+ NPs described above indicate that these phosphors can be used as potential radioluminescent materials for phosphor converted light emitting diodes and X-ray screen.

Environmentally friendly molten salt synthesis of high-entropy AlCoCrFeNi alloy powder with high catalytic hydrogenation activity

A molten salt synthesis method was used to prepare high-entropy AlCoCrFeNi alloy powder with a high specific surface area of 67.5 m2/g, exhibiting remarkable catalytic activity in the hydrogenation of p-nitrophenol by NaBH4. The life cycle assessment of the proposed method indicated that AlCoCrFeNi production was associated with greenhouse gas emission of 125 kgCO2e/kg-product, whose main contributors were CaH2 and citric acid used during the precursor's reduction and formation, respectively. On the other hand, that for a previously reported dealloying method was 277 kg CO2e/kg-product. Thus, a minimum of 54% greenhouse gas emission reduction compared to the conventional dealloying method is achievable in the proposed molten salt method. The results indicated the possible environmentally friendly production of high-surface-area, high-entropy alloy powders suitable for industrial applications.

One step molten salt synthesis of nickel nanoparticles incorporated on graphene sheets as non-precious and an effective electrocatalyst for methanol oxidation

Fabricating electrocatalysts based on metal nanoparticles (NPs)/carbon nanomaterials by a facile and cost-effective method have attracted serious attention in the past several years to expand their applications. This study aimed to prepare an effective electrocatalyst based on nickel nanoparticles decorated graphene sheets (NiNPs@Gr) by molten salt synthesis method and to clarify its advantages compared to the calcination method without molten salt. The microscopic characterization revealed that the calcination of nickel/carbon precursors in the molten salt medium resulted in nickel NPs supported on graphene sheets, whereas produce NPs with larger sizes supported on porous carbon without molten salt. X-ray diffraction analysis showed that the catalysts prepared by the molten salt method (NiNPs@Gr-S1 and NiNPs@Gr-S2) resulted in nickel NPs with a mixture of crystalline structures (face-centered cubic and hexagonal close-packed). The electrocatalytic activity of NiNPs@Gr-S1 and NiNPs@Gr-S2 toward methanol oxidation was higher than that of the NiNPs@C catalyst prepared without molten salt. The maximum peak current density of NiNPs@C, NiNPs @Gr-S1, and NiNPs @Gr-S2 are 30, 80, and 81.5 mA/cm2, respectively. Moreover, electrocatalysts derived from molten salt synthesis demonstrated significantly increased electrocatalytic stability. These results emphasize the synthesis of graphene nanosheet-supported Ni NPs in a single step without any additional chemicals, which makes such a strategy promising in trust acquisition for investors in large-scale production of NiNPs@Gr.

Effects of synthesis methods on the structural and magnetic properties of double perovskite Sr2CrReO6 oxide powders

Double perovskite Sr2CrReO6 (SCRO) powders were prepared using a sol-gel process and molten-salt synthesis (MSS) method and then followed by annealing at different temperatures in N2 (or Ar) atmospheres. They were characterized by powder X-ray diffraction and then followed by structural Rietveld refinements. The results reveal that at room temperature all the SCRO powders crystallize in a tetragonal phase structure with space group of I4/m. The Cr/Re cationic ordering degrees (η) at B-site in the sol-gel derived SCRO powders annealed in Ar and N2 atmospheres, were about 68.9 % and 45.3 % respectively. The η values for the SCRO powders prepared by MSS method under the molar ratios of product-to-flux with 1:100, 1:80, and 1:50, were 67.4 %, 57.0 % and 54.3 %, respectively. All the SCRO powders exhibited ferromagnetic behaviors at room temperature and their saturation magnetization (MS) values at 2 K were in range of 0.52–0.67 μB/f.u., smaller than the theoretical value of 1.0 μB/f.u. That can be ascribed to the anti-site defects as well as the surface spin disorders in these SCRO powders. The sol-gel derived SCRO powders had a bead-like morphology and their average composition is slight Cr-rich and Re-deficient with a chemical formula of Sr2Cr1+xRe1−xO6+δ, whereas the SCRO powders prepared by MSS method exhibited a spherical morphology and their average composition is slight Cr-rich and Sr-deficient with a chemical formula of Sr2−yCr1+yReO6+δ. XPS spectra confirm a mixed valence states of Cr3+ and Cr6+ ions in the sol-gel derived SCRO powders, while only Cr3+ ions present in the SCRO powders prepared by MSS method. The Sr2+ ions and a mixed Re4+ and Re6+ ions exist in all the SCRO powders, and three kinds of oxygen species are present as lattice oxygen (O2-), adsorbed oxygens, and the oxygens in hydroxyl groups, respectively. The sol-gel derived SCRO powders had a higher MS but a smaller Hc in comparison with the powders prepared by MSS method, which enables them to have promising applications in future spintronic devices.

Synthesis of CaCu3Ti4O12 Micron-cubes and rods via high proportion molten salt method

CaCu3Ti4O12 (CCTO) particles were produced from a CuO–CaCO3–TiO2 peroxo-hydroxide precursor material in NaCl–KCl and Na2SO4–K2SO4 salt mixtures via the molten-salt synthesis method at different salt-to-precursor mass ratios. Regular-shaped CCTO particles of cubes, rods, and polyhedrons can be obtained at large salt-to-precursor mass ratios of above 50:1. With the extension of sintering time, the particle shape is more regular and the size is larger. Long micro rods with a length of about 53 μm can be obtained at a mass ratio of 125:1 and a long sintering time of 72 h in sulfate salts. The formation mechanisms are also discussed and the results suggest that a large salt-to-precursor mass ratio may provide a sufficient number of Na − K ions to sufficiently modify the particle shape and form regular-shaped cubes and rod-like particles. At the same time, CCTO ceramics synthesized by Na2SO4–K2SO4 molten-salt method show good dielectric properties, with a dielectric constant higher than 104 and a loss factor less than 0.45 in the range of 20 Hz to 1 MHz.

Synthesis of Ti3SiC2 MAX phase powder through molten salt method

AbstractTitanium silicon carbide (Ti3SiC2) MAX phase powder was synthesized from elemental reactants using the molten salt synthesis (MSS) method. Optimum experimental parameters were also investigated to determine the purity and synthesis pathway of the Ti3SiC2 MAX phase. The results showed that Ti3SiC2 was not synthesized using carbon black as the carbon source in the starting materials because of the high quantity of TiC formed along with the TiSi2 silicide phase. However, Ti3SiC2 was successfully synthesized in a relatively high purity (93%) at 1200°C for 2 h using graphite as the source of carbon because of the formation of TiC and Ti5Si3 intermediate phases. The Ti5Si3 silicide phase was found to play a crucial role in the formation of the Ti3SiC2 MAX phase using the MSS method. Moreover, applying a pressure of 150 MPa to the prepared samples and using the eutectic mixture of NaCl–KCl (molar ratio: 1:1) instead of NaCl also resulted in the higher formation of the Ti3SiC2 MAX phase. The formation mechanism of Ti3SiC2 was determined to be the reaction among Ti5Si3, TiC, and residual carbon through the template‐growth and dissolution–precipitation mechanisms that occurred at different stages of the synthesis process.

Preparation and characterization of porous hydroxyapatite reinforced with hydroxyapatite whiskers

In this study, porous hydroxyapatite scaffolds reinforced with whiskers were fabricated. HAp whiskers were produced by the molten salt synthesis method using 5 different salt-HAp mixtures. The mixtures placed in alumina crucibles were heated to 900 oC with a heating rate of 5 oC/min in a muffle furnace and kept at this temperature for 2 hours and then cooled in the furnace. To clean the HAP crystals formed in the alumina crucibles from the reaction residues, they were washed many times with distilled water heated to 100 oC and filtered. HAp whiskers were mixed with HAp powder in certain proportions, and porous HAp reinforced with HAp whiskers were fabricated by using the sponge replica method. The synthesized whiskers and the scaffold structures were characterized by Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy, X-ray diffractometry, Compression test, and porosity measurement method.XRD analysis of synthesized whiskers confirmed the presence of HAp. SEM images showed interconnected pores in the samples, with pore sizes larger than 100µm. The compressive strengths of the samples were calculated from the stress-strain plateau average. The highest and the lowest compressive stress were calculated as 0,125 and 0,050 MPa respectively. The maximum and minimum porosities of the samples reinforced with whiskers were found to be 67,56% and 61,92%, respectively.

Molten-salt synthesis of manganese-doped intermetallic TiFexMn(1−x) nanoparticles from oxide precursors

Manganese-doped intermetallic TiFexMn(1−x) nanoparticles (NPs) were synthesized by a molten-salt synthesis method using TiO2, FeSO4•7H2O, and Mn(NO3)2•6H2O as the raw materials. The Ti–Fe–Mn oxide precursors prepared from the raw materials were efficiently reduced at temperatures as low as 600 °C in molten LiCl in the presence of CaH2 as the reducing agent. This resulted in the formation of TiFexMn(1−x) NPs exhibiting few impurities (e.g., TiFe2 or/and TiFe39). Increase in the Mn content led to peak shifts in the X-ray diffraction (XRD) patterns, indicating good incorporation of Mn into the cubic CsCl-type structure of intermetallic TiFe to form a solid solution. Nano-sized particles of< 100 nm were clearly observed in the obtained powders by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, homogeneous distribution of the constituent elements (i.e., Ti, Fe, and Mn) was confirmed by energy dispersive X-ray (EDX) spectroscopy. Finally, the hydrogen absorption properties of the prepared TiFe0.7Mn0.3 NPs were analyzed. Notably, with the exception of micron-sized TiFe0.7Mn0.3 prepared by common arc melting, the generated NPs exhibited almost no hydrogen absorption. The results obtained herein demonstrated the importance of particle size in activating TiFe-based hydrogen absorption materials.

Structural Evolution of Mg-Doped Single-Crystal LiCoO2 Cathodes: Importance of Morphology and Mg-Doping Sites

Layered lithium cobalt oxide (LiCoO2, LCO), which serves as a structural motif for the widely adopted layered cathodes in lithium-ion batteries, has a long history, and its unstable phase transition during high-voltage operation (∼4.5 V) remains an intractable problem. Many research strategies, such as surface coating and immobile ion doping, have been proposed to address this issue, but a clear understanding of the effects has not been demonstrated because of various potential parameters (e.g., particle size, shape, and dopant content). Herein, we report a molten salt synthesis method that produces sphere-like single-crystal magnesium (Mg)-doped LCO. In situ X-ray diffraction and X-ray absorption fine structure analyses confirmed that the lattice strain was effectively alleviated by the effects of both the particle shape and Mg doping compared to the plate-like and sphere-like single-crystal LCO samples. Furthermore, the preference for Mg doping in the Co site (3b) rather than in the Li site (3a) in the LCO framework is systematically revealed, and a clear understanding of Mg doping that suppresses the monoclinic phase transition is discussed in detail.