Hydrothermal Synthesis of SrTiO₃: Role of Interfaces

Abstract

The hydrothermal synthesis of SrTiO3 in a Sr­(OH)2/NaOH solution by reaction of four different single crystalline titanium precursors (anatase, rutile, sodium titanate, and hydrogen titanate) having the same nanowire morphology was investigated under stagnant fluid conditions. Owing to the low solubility and dissolution rate of the parent phases, the reaction mainly occurs in a thin interfacial fluid layer. The new phase only grows on the substrate surface, and the morphology evolution is largely controlled by the interface through the coupling of substrate dissolution and SrTiO3 crystallization. The pseudomorphic replacement of the precursor by the product occurs if complete surface coverage is attained. Depending on the crystallographic matching, the parent crystal can either transform in a mesocrystal as happens with anatase via a topochemical transformation or in a polycrystalline product as observed with sodium titanate. In contrast, if the product grows in the form of isolated particles or with dendritic morphology, as in the case of hydrogen titanate and, to a lesser extent rutile, the new compound will not inherit the precursor morphology. When well-defined interfaces are missing, as happens when amorphous titanium hydroxide gel suspensions are used as precursors, the crystallization of SrTiO3 occurs by a completely different pathway, i.e., oriented self-assembly of nanocrystals in mesocrystals.

Effect of Dopant Loading on the Structural and Catalytic Properties of Mn-Doped SrTiO3 Catalysts for Catalytic Soot Combustion

“…Table 2 Figure 4 shows the N 2 adsorption-desorption isotherms. All samples have typical type IV isotherm showing a hysteresis loop at high relative pressures, which is associated with capillary condensation representative of mesoporous materials [24][25][26][27][28]. This is confirmed by the mean pore size shown in Table 2, where all samples have a pore size in the range of mesopores (2-50 nm).…”

“…Dendritic morphology is clearly detected for all samples; dendrites are composed by a main long branch approximately 0.5 µm in length. The formation of dendrites is associated with the diffusion process during the hydrothermal reaction [24,25]. (Figure 2d), but in sample Mn4, some content of Mn below the 4 wt % is detected.…”

Perovskite Structure Associated with Precious Metals: Influence on Heterogenous Catalytic Process

“…One of the most interesting advantages in the use of this method to obtain semiconductor materials is the possibility of producing the same material with different morphologies. Spherical shaped SrTiO 3 with sponge-like mesoporous morphology [90], cubic-like SrTiO 3 [91,92], SrTiO 3 dendritic particles, among other SrTiO 3 morphologies, can be obtained from hydrothermal method [93] (Figure 4). In this sense, the syntheses parameters can be controlled in order to produce a material with different morphology.…”

“…In this sense, the syntheses parameters can be controlled in order to produce a material with different morphology. The work conducted by Kalyani et al is a good example of how synthesis parameters influence the product obtained since the authors developed a comprehensive study on the SrTiO 3 growth mechanism as a function of the synthesis conditions [93]. After the synthesis, the surface of the particles can be easily decorated with a precious metal through a chemical solution process; in some cases, the metal deposition process may be photo-assisted [83,84].…”

Single-step hydrothermal synthesis of strontium titanate nanoparticles from crystalline anatase titanium dioxide

“…Multiple wet chemical routes have been extensively developed to resolve these disadvantages in recent years, including chemical precipitation method [5], sol-gel method [6], microwave-assisted synthesis [7,8], solvothermal reaction [9] and hydrothermal reaction [10,11]. Among these synthesis methods, the hydrothermal reaction is one of the most promising preparation methods to obtain nanoparticles having narrow particle size distribution, small particle size, high crystallinity, good purity and well-controlled morphology.…”