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Highlights: [•] Amorphous precursor was used to prepare titanate nanostructure by hydrothermal process. [•] Morphology evolution from nanoparticles to nanosheets and then nanowires was observed. [•] It provides direct evidence to support the dissolution/recrystallization mechanism. [Copyright &y& Elsevier]

A facile hydrothermal method has been developed to synthesize single-crystal ferroelectric PT nanoplates by using K2Ti6O13 nanowires as synthetic precursor. The PT nanoplates with dominant {001} facets have the side length of 500–700 nm and height of 100–150 nm. Piezoelectric force microscopy (PFM) results demonstrated that the PT nanoplates show obvious piezoelectric and ferroelectric activity. Moreover, the crystal growth of the PT nanoplates has been discussed. The results revealed that the gradual dissolution of K2Ti6O13 nanowires in alkali solution and the template of lead oxide are essential to the formation of PT nanoplates. [ABSTRACT FROM AUTHOR]

Abstract: A simple approach based on an organically modified sol–gel process has been developed to fabricate PbTiO3 (PT) nanocrystals on Si (100) substrate, where the amorphous powder modified by acetylacetone (acac) was used as precursor. After dropping the amorphous powder precursor prepared by freeze-drying process, PT nanocrystals on Si (100) substrate were obtained after heat treatment at 720°C for 30min in air. PT nanocrystals have been detected by XRD to be tetragonal perovskite structure. With the increase of acac/Pb molar ratio, the relative (100)/(001) diffraction peak intensity gradually increases, which probably suggested an oriented growth of PT nanocrystal along [100] on Si (100) substrates. In addition, Atomic force microscopy (AFM) results indicated that the height and the average lateral size of PT nanocrystal increased and then decreased as the acac/Pb molar ratio increased. Piezoelectric force microscopy (PFM) results demonstrated that all the samples show obvious piezoelectric activity. These results implied that the acetylacetone molecular mediated the growth of PT nanocrystals on Si (100) substrates possibly by the acac/Pb molar ratio. This simple method has been suggested to be attractive for tailoring an oriented growth of the nanostructures of perovskite oxide systems on Si substrates. [Copyright &y& Elsevier]

Abstract: We report the controlled hydrothermal growth of rutile TiO2 nanorods on Si wafers by using an anatase TiO2 nanodot film as an assisted growth layer. The anatase nanodot film was prepared on the wafer by phase-separation-induced self-assembly and subsequent heat-treatment at 500°C. The nanodots on the wafer were then subjected to hydrothermal treatment to induce the growth of rutile TiO2 nanorod films. The size and dispersion density of the resulting TiO2 nanorods could be varied by adjusting the Ti ion concentration in the growth solution. The TiO2 nanorods were of the rutile phase and grew in the [001] direction. The growth mechanism reveals that the growth of the rutile nanorods was wholly dependent on the existence of rutile TiO2 seeds, which could be formed by the dissolution–reprecipitation of the anatase nanodots during hydrothermal treatment or under the high-temperature conditions of the subsequent heat-treatment of the as-prepared nanodots. In controlling the rutile nanorod growth, the anatase nanodots show more efficiency than a dense anatase film. Preliminary evaluations of the rutile nanorod films have demonstrated that the wettability changed from highly hydrophobic to superhydrophilic and that the photocatalytic activity was enhanced with increasing nanorod dispersion density. [Copyright &y& Elsevier]

Abstract: Rutile TiO2 nanorod films have been successfully prepared on titanium substrate via a hydrothermal method using Tetra-n-butyl titanate as Ti source in the presence of concentrated hydrochloric acid. The effect of Ti substrate annealing treatment and adding of additional alkali metal chlorides in hydrothermal solution on the growth of TiO2 nanorod films has been studied using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and water contact angle measurement. The growth mechanism of the TiO2 nanorods on Ti substrate has also been discussed. It has shown that the initial rutile film transformed from anatase promotes the nucleation and epitaxial growth of rutile TiO2 nanorods. The superior wettabilities of the TiO2 nanorods resulted from treatments of vacuum and ultraviolet show great potential for applications in orthopaedic, dental implants, and possible photocatalysis. [Copyright &y& Elsevier]

Abstract: Ring- and single-crystal-like superstructures of Fe-doped PbTiO3 nanocrystals have been prepared by a simple hydrothermal method using (poly ethylene glycol) (PEG) as a surfactant. Two oriented-attachment forms of the nanocrystals favor the formation of the rings in view of geometry. Magnetism measurement shows that Fe-doped PbTiO3 sample is ferromagnetic even at room temperature. It is proposed that the magnetic dipole interactions and the presence of PEG molecules could together contribute to the formation of ring- and single-crystal-like superstructures composed of Fe-doped PbTiO3 nanocrystals. [Copyright &y& Elsevier]

Abstract: Single-crystal SrTiO3 dendritic nanostructures were synthesized for the first time via a simple hydrothermal method without any surfactant. Structure characterizations suggest that the SrTiO3 dendrites show preferential orientation along [110]. Additionally, it is found that KOH concentration plays an important role in the formation of SrTiO3 dendrites, and the morphology of SrTiO3 crystallites can vary from cubic-like, star-like to dendritic shape. A rational mechanism is proposed to illustrate the growth of SrTiO3 dendrites. [Copyright &y& Elsevier]

A new method has been developed to synthesize barium titanate (BaTiO3) nanoparticles with a narrow size distribution under ambient conditions at room temperature. The as-prepared BaTiO3 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, high-resolution TEM, and selected area electron diffraction. On the basis of the characterizations, it was found that the particle size could be easily tuned by adjusting the experimental parameters, such as the solvent component and reaction time. The basicity of the organic solvent was considered to play an important role in the room-temperature synthesis and the solvent molecules had a strong influence on the crystal growth of BaTiO3 nanoparticles. The BaTiO3 nanoparticles obtained were well dispersed and possessed a cubic perovskite structure at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: The size-controlled synthesis of barium titanate (BaTiO3) nanocrystals has been achieved by a hydrothermal route with Fe doping and ethylenediamine (en) addition. The as-synthesized BaTiO3 nanocrystals were characterized with XRD, SEM, TEM, and HRTEM. The results revealed that the average particle sizes of Fe-doped samples were reduced compared to that of the sample without Fe doping, suggesting that the doping ions inhibited the crystal growth. It was also found that the average particle size decreased as the Fe doping concentration increased. Furthermore, the addition of en, which served as both solvent and capping agent, could suppress the particle growth and lead to the change in particle shape from sphere to cube by a confined effect. [Copyright &y& Elsevier]

The Si–C–H thin films were deposited at 300 °C by plasma enhanced chemical vapor deposition (PECVD) and around 600 °C by pyrolysis CVD, in which C2H4 and SiH4 were used as the resource gases and hydrogen as the carrying vehicle. The formation of micro-crystals in the Si–C–H films was investigated by TEM, IR spectroscopy and electrical resistivity measurements. The results show that many silicon nano-crystalline particles are embedded and distributed uniformly in the amorphous matrix of the Si–C–H thin film. A higher content of C2H4 results in a lower crystallinity of the film deposited both by PECVD and pyrolysis CVD. The crystal grows more easily in the film deposited with C2H4–SiH4 at high temperature around 600 °C by pyrolysis CVD than that deposited at 300 °C by PECVD. The resistivity of the film by pyrolysis CVD at high deposition temperature is about five orders of magnitude lower than that by PECVD at low deposition temperature. The SiC crystalline phase trends to form quite possibly in the Si–C–H thin film deposited at 630 °C by pyrolysis CVD. The expressions of the crystallinity and resistivity as functions of the content of C2H4 are theoretically deduced. The theoretical curves are showed to be very coincident with the experimental results in the Si–C–H thin film. The crystallinity of the film rests mainly with the nucleation rate of silicon phase that is dependent on the content of C2H4 in deposition source gases. The resistivity behavior of Si–C–H thin film matches with the parallel model of the two phase events, where the contribution of crystalline phase is appropriate to the contact probability among the silicon crystals and compatible with homogeneous distribution of the particles embedded in matrix. [Copyright &y& Elsevier]