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One dimensional ferroelectric materials have important applications in the field of micro-nanoelectronic devices. In this work, three kinds of ferroelectric niobates (KNbO3, KSr2Nb5O15, K0.5Bi2.5Nb2O9) with different structures (perovskite, tetragonal tungsten bronze-TTB, bismuth niobates layer structure-BNLS) have been synthesized by using the one dimensional Nb2O5 as precursor through topochemical molten salt synthesis (TMSS) method. Among them, perovskite-KNbO3 can maintain the one dimensional morphology of the Nb2O5 template. TTB-KSr2Nb5O15 partly inherited the template morphology, but BNLS-K0.5Bi2.5Nb2O9 had the totally different morphology with the Nb2O5 precursors. Through the comparison and analysis of the crystal structure of the three target noibates, it indicated that the inheritance of template’s morphology depended on the product’s reassembly modes of the [NbO6] octahedron. Perovskite type ANbO3 (A = K, Na, Li) with the corner-shared [NbO6] octahedron was most conducive to the succession of the morphology of the Nb2O5 template in the three products. Relevant results can help us to choose templates and target products more rationally for synthesis of one dimensional nanomaterials through TMSS method.

The role of reactive environment and hydrogen specifically in growth and structure of molybdenum selenide (MoSe2) nanomaterials is presently debated, and it is not clear whether hydrogen can promote the growth of MoSe2 sheets and alter their electronic properties. To find efficient, convenient methods for controlling the nucleation, growth and resultant properties of MoSe2 nanomaterials, MoSe2 nanoflakes were synthesized on silicon substrates by hot filament chemical vapor deposition using molybdenum trioxide and selenium powders in pure hydrogen, nitrogen gases and hydrogen-nitrogen mixtures. The structures and composition of synthesized MoSe2 nanoflakes were studied using the advanced characterization instruments including field emission scanning electron microscopy, micro-Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectrometry. The analysis of the growth process indicates that hydrogen can improve the formation of MoSe2 nanoflakes and significantly alter their properties due to the high reduction capacity of hydrogen and the creation of more nucleation centers of MoSe2 nanoflakes on the silicon surface. The study of photoluminescent (PL) properties reveals that the MoSe2 nanoflakes can generate a strong PL band at about 631 nm, differently from the plain MoSe2 nanoflakes. The major difference in the PL properties may be related to the edges of MoSe2 nanoflakes. These results can be used to control the growth and structure of MoSe2-based nanomaterials and contribute to the development of advanced MoSe2-based optoelectronic devices.

A kind of lead-free nanocrystalline powder, (Li 0.06 Na 0.47 K 0.47 )NbO 3 (LNKN), has been prepared by a newly developed sol–gel method using Nb 2 O 5 as the Nb source. Phase analysis, microstructure and morphology of the powder were determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, transmission electron microscope (TEM) and high-resolution transmission electron microscopy (HRTEM). The experimental results showed that pure perovskite phase was formed at the temperature as low as 500 °C. Besides, the obtained powder belonged to tetragonal symmetry, and the mean particle size was as small as 20 nm. It is believed that the high-quality gel precursor and low processing temperature play a key role in the formation of the LNKN nano-particles. The process developed in this work was convenient to realize the mass production of LNKN nano-powders at low cost.

A sol–gel-hydrothermal method has been adopted to synthesize the shape-controlled SrTiO 3 crystallites. A series of shape evolutions of SrTiO 3 crystallites varied gradually from the unfeatured conglomeration through eight-pod star-shaped particles to cubic crystals and have been recorded based on transmission electron spectroscopy (TEM) and scanning electron microscopy (SEM) observations. The faster growth rate along [1 1 1] direction in the SrTiO 3 lattice resulted in the (1 1 1) plane disappearing, while (1 0 0) plane remained to form SrTiO 3 cubes owing to the relative lower growth rate. The experimental results suggest that the building blocks with desired architecture can be selectively synthesized by programming the growth conditions in the initial synthetic scheme.

Using niobium-chelated precursor, a novel method for synthesizing layered niobate (K4Nb6O17) thin films was developed. After annealing at 600 °C or above, the nanostructured K4Nb6O17 thin films with (0 4 0) preferred orientation were successfully produced by sol–gel process. XPS measurement showed that the atomic ratio of K:Nb:O in the thin film was 4.08:5.99:16.77, which was in good accordance with the stoichiometry of K4Nb6O17. Varying with annealing parameters, the layered structure of the thin films altered and the hydrated layered K4Nb6O17·3H2O thin films presented while low pyrolysis temperature was applied. The hydrogen evolution from water decomposition showed the excellent photocatalytic properties of the films. The static hydrogen evolution for the thin film annealed at 600 °C reached 105 μmol cm−2 h−1.

In this work, we used a sol–gel-derived layer to control the morphology and crystallinity of the fresnoite thin films produced by magnetron sputtering. Atomic force microscope (AFM) and Raman scattering spectra showed that the sol–gel-derived layer improves the crystallinity and morphology of the films as-sputtered. Compared to the film without the layer which gives a blur image of grains, fresnoite film with the layer presented sharp boundaries and distinct shapes, which is referred to the imprint of the layer's structure. Meanwhile, the difference in X-ray diffraction patterns and Raman spectra showed the different crystallinity of the films with or without the layer. It is suggested that the nanocrystalline layer fabricated by sol–gel method provides the nucleation site, and lower the energy barrier of the crystal growth in the sputtering of the thin films, thus making the thin films sputtered onto it with developed grains and the structural aspect of the layer.

A kind of novel lead-free ferroelectrics, potassium bismuth titanate, K 0.5 Bi 0.5 TiO 3 (KBT), has been prepared by the sol–gel process. The amorphous dried gels were first transformed into Bi 2 Ti 2 O 7 phase at low heat-treated temperature and as the temperature increased to 700 °C, only pure KBT phase can be observed and there was no evidence of second phase. KBT ferroelectric ceramics were fabricated from the natural sintering of 700 °C-treated powders, which have a particle size of 100–200 nm. The KBT ceramics sintered at 1050 °C showed typical characteristics of relaxor ferroelectric, and the dielectric properties were better than that prepared by a solid-state reaction method.

Tantalum pentoxide (Ta 2 O 5 ) films with high 〈0 0 1〉 orientation have exceptionally high dielectric constant. Usually, oriented Ta 2 O 5 films were fabricated by post-annealing. In this paper, as-deposited Ta 2 O 5 films with high 〈0 0 1〉 orientation were sputtered at low temperature with substrate bias. The orientation of the films is modified to be better with the bias being increased. The bias effect on the orientation of the films is discussed in details.

A new phase of cadmium titanate was prepared by hydrothermal method under low temperature of 120°C. The electron diffraction investigation showed that the structure of the new phase is hexagonal with lattice parameters a = b =5.2099 A and c =4.6811 A, which have been calibrated by its X-ray diffraction pattern. The X-ray photoelectron spectroscopy results suggested that the new phase can be described as CdTiO 3 . Furthermore, it was observed that the post-annealing at 700°C and 1050°C led to the transition of the new phase to the known ilmenite and then perovskite phase, respectively .