Fabrication and piezoresponse properties of {100} BaTiO3 films containing highly ordered nanocube assemblies on various substrates

Liu

Itasaka

et al. 2020

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A-site substituted (Ba 1¹x ,Sr x )TiO 3 nanocubes (BS x T NC; x is Sr ratio) were synthesized by hydrothermal process with surfactant and additives. X-ray diffraction profiles of BS x T NCs showed single-phase of perovskite. Size of BS x T NCs was decreased with increasing Sr content under same hydrothermal condition. When synthesis temperature increased, size of BS x T NCs was enlarged. It revealed that the size of BS x T NCs was able to be controlled by optimizing the hydrothermal conditions. However, inhomogeneous substitution was observed by scanning transmission electron microscopy with energy dispersive X-ray spectroscopy. It suggested that reaction rate of Sr ions to form perovskite structure was faster than that of Ba ions under hydrothermal condition. Threedimensional (3D) assemblies of BS x T NCs after heat-treatment at 850°C had obscured interfaces between the NCs. Raman spectroscopy of NC assemblies revealed that symmetry of BS x T NCs differed from that of BaTiO 3 (BT) NCs and did not change after heat-treatment at 850°C. Piezoresponse curves became slim hysteresis behavior with increasing Sr ratio. These results suggested that Sr substitution of BT NCs caused phase transition from ferroelectric to paraelectric phase in 3D assemblies.

Section: Methodsmentioning

confidence: 99%

Hydrothermal synthesis of A-site substituted BaTiO<sub>3</sub> nanocubes

Liu

Itasaka

et al. 2020

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“…In order to measure Raman spectra of BT and BZT 0.2 NCs, these NCs were assembled by slow-rate dip-coating method using the NC dispersed mesitylene solution. 13) These assemblies for Raman spectroscopy were irradiated by UV light for 2 h and dried at 200°C for 1.5 h in oven.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and characterization of barium titanate-based solid solution nanocubes

Kato

2016

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Ba(Zr x ,Ti 1¹x )O 3 nanocubes (BZT x NCs) were synthesized by hydrothermal reaction with titanium and zirconium aqueous compounds and surfactants. The nanocubes were assembled on the substrates by dropping-drying method. The microstructures of the nanocube were evaluated by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The ordered assemblies of the NCs were yielded on the substrate when Zr contents were below 0.2. BZT 0.2 NCs had narrow size distribution about 20 nm observed by FE-SEM and TEM. On the other hand, BZT 0.5 and BaZrO 3 NCs were attached each other and they formed large cube above 100 nm. Perovskite phase was confirmed in all BZT x NCs by X-ray diffraction. Lattice constant of BZT x NCs increased linearly with increasing Zr contents. The composition of BZT 0.2 NCs were calculated by X-ray photoelectron spectroscopy. These results suggest that the ratio of Ba:Zr:Ti is nearly equal to the nominal ratio. Crystallographic phase of BaTiO 3 and BZT 0.2 NCs was characterized by Raman spectroscopy under various measurement temperatures.

“…26),27) BT NCs were dispersed in mesitylene (1,3,5-trimethylbenzene) by ultrasonic treatment. The mechanism of capillary-force-assisted self-assembly is shown in Fig.…”

Section: Hydrothermal Synthesis Of Bt Ncs With Aqueous Compounds and mentioning

confidence: 99%

Processing of dielectric nanocube 3D-assemblies and their high electrical properties for next-generation devices

2016

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Nanocrystals have great potential to achieve extremely high electrical properties induced by their shapes, size, and facet surfaces. BaTiO 3 nanocube (BT NC) 3D-assemblies with numerous interfaces and closely packed nanostructure are attracting as materials for next-generation dielectric devices due to their advantages for enhancing dielectric properties such as high packing density, high orientation, and interaction of the interfaces between the nanocubes. In this paper, we review our studies on the solutionbased processing of BT NC 3D-assemblies and their high dielectric properties. BT NCs 15 nm in size have already been synthesized by the hydrothermal method with aqueous compounds and surfactants. As NCs were well-dispersed in non-polar organic solvent, BT NC 3D-assemblies were fabricated by a dip-coating process while controlling the up-stroke rate of the substrate and evaporation rate of the solvent. The capillary force generated through the dip-coating assisted in ordering the NCs. We also successfully fabricated micro-patterning of BT NC assemblies using polymeric micro-molds and removing them by a chemical wet process. This soft process has the great advantages of avoiding both etching damage occurring in the dry process and the clamping effect of substrate. The ordering and cubic shape of the BT NC 3D-assemblies were maintained under heattreatment up to 900°C. The local strain at the BT NC interfaces was induced by epitaxial attachment with small angle tilting between neighboring NCs. The dielectric constant of the BT NC assembly heat-treated at 850°C achieved above 4000 with relatively low loss tangent below 7%. The local strain at the interfaces seemed to enhance the dielectric properties without the nanosize effect and thickness effect of dielectric materials.