Anisotropy in morphology and crystal structure of BaTiO3 nanoblocks

Abstract

a b s t r a c tSingle crystalline {100} dominant BaTiO 3 nanoblocks were synthesized by the hydrothermal method using aqueous sources of Ba and Ti, and organic additives. BaTiO 3 nanoblocks with neat surface and standard corner angle show two kinds of morphology, cubic and cuboid shapes. Based on TEM images of BaTiO 3 nanoblocks, the percentage of nanocuboids improved from 24.3% to 51.8%, as the average size of nanoblocks varied from~15 nm to~25 nm. The asymmetric morphology of BaTiO 3 nanocuboids reveals an anisotropic growth pattern. One straightforward method was employed to discuss the crystal phase of BaTiO 3 nanocuboids by using the HR-TEM images and the corresponding FFT patterns. The d spacing of {100} crystal planes show diverse values. The ratios of d spacing of (100) crystal plane and the perpendicular (001) plane are larger than one. The short edge direction in BaTiO 3 nanocuboids coincides with their [001] crystal orientation. According to the enlarged FFT filtered HR-TEM images, the shape and oriented array of the unit cells in nanocuboids played a crucial role on the formation of anisotropy in morphology. Co-considering the DSC result, the findings indicate the existence possibility of tetragonal phase in BaTiO 3 nanocuboids with b30 nm size.

Structural Instability in Electrically Stressed, Oxygen Deficient BaTiO3 Nanocrystals

“…Compared with the known lattice parameters in the common polymorphic forms of BaTiO 3 , the cyan circled spots can be assigned to (001) planes and the yellow circled spots to (101) planes of BaTiO 3 . [18] The purple circled spots is likely from (100) planes which is 6.5% smaller than the assigned d-spacing of (001) planes. When a zone axis is tilted away from the electron beam, up to 10% error can be found when the lattice spacings are measured from the fringes in high resolution TEM micrographs.…”

Nucleation and Growth Mechanism of Barium Titanate Nanoblocks in Hydrothermal Process Using Aqueous Titanium Compound

“…The synthesis recipe has been published in previous articles. 9 The sampling hydrothermal vessel is equipped with two thermocouples, one gas pressure gauge, and one sampling port. The thermocouples of the hydrothermal vessel are inserted into the inside of the autoclave through the sealed metal pipe of the vessel.…”

“…The synthesis recipe has been published in previous articles . The sampling hydrothermal vessel is equipped with two thermocouples, one gas pressure gauge, and one sampling port.…”

“…5−8 Numerous studies verified that hydrothermal synthesis was one promising method to produce fine and pure monodisperse BT nanocrystals with controllable morphology. 7,9,10 Due to sealing the reaction system with natural pressure, the hydrothermal growth mechanism of BT nanomaterials is ambiguous and attracts lots of attention. O'Hare et al employed a time-resolved powder neutron diffraction method to confirm the dissolution− precipitation process of BT.…”

“…Since its discovery in the 1940s, barium titanate (BT) has been widely applied in the preparation of multilayer ceramic capacitors (MLCCs), embedded capacitors in printed circuit boards, microwave devices, and electro-optical devices. − In order to meet the requirement of scientific and industrial advancement, many wet chemical methods were developed to synthesize highly qualified BT nanocrystals. − Numerous studies verified that hydrothermal synthesis was one promising method to produce fine and pure monodisperse BT nanocrystals with controllable morphology. ,, Due to sealing the reaction system with natural pressure, the hydrothermal growth mechanism of BT nanomaterials is ambiguous and attracts lots of attention. O’Hare et al employed a time-resolved powder neutron diffraction method to confirm the dissolution–precipitation process of BT .…”