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Transition metal oxide nanowires

a metal oxide nanowire and transition metal oxide technology, applied in the field of transition metal oxide nanowires, can solve the problems of large and expensive magnetic field sensors in their products, poor crystalline quality of highly agglomerated samples, and deformation of the whole crystal

Inactive Publication Date: 2005-03-24
PRESIDENT & FELLOWS OF HARVARD COLLEGE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The same distortion of the unit cell, added together coherently throughout the crystal, also results in the deformation of the whole crystal that leads to piezoelectricity.
These industries currently employ large and expensive magnetic field sensors in their products.
However, existing preparation of nanocrystal solids of ferroelectric oxides for example, such as sol-gel synthesis and co-precipitation have yielded highly agglomerated samples with poor crystalline quality.
Despite intensive experimental efforts, however, a general method to synthesize well-isolated crystalline nanostructures of for example, perovskite oxides has been lacking.

Method used

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Examples

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example 1

BaTiO3 Nanowire Synthesis

Three mmol (1.62 g) of barium titanium isopropoxide complex (precursor) is added to 0.3 mmol (0.084 g) of oleic acid (a coordinating ligand) in 10 mL of heptadecane (solvent) (10:1 molar ratio) under inert atmosphere. The reagent mixture is then stirred and heated up to 100° C., and 4 mL of a 3% H2O2 solution is injected into the mixture. After injection, the reaction mixture is heated to 280° C. for 3-12 hours. During this time, the reaction mixture turns from yellow to white as the vigorous bubbling that follows injection subsides. After 3 hours, the reaction is cooled to room temperature. The remaining solution is then washed with methanol and centrifuged to flocculate the nanowires. The supernatant is discarded. The flocculate is then washed with hexane and centrifuged repeatedly to eliminate any remaining heptadecane. After the final centrifugation step, the supernatant is discarded, and the precipitate is dried under vacuum, producing dried nanowire...

example 2

Characterization of BaTiO3 Nanowires

The analysis using scanning electron microscopy (FIGS. 1 and 2), transmission electron microscopy (FIG. 3), X-ray diffractometry (FIG. 4) reveals that the reaction products are single-crystalline BaTiO3 nanowires with diameters from 3 nm to 100 nm and lengths up to >10 μm.

example 3

Preparation of Precursor Barium Alkoxide Precursors

The precursors were synthesized by the following procedure in an inert atmosphere: 65.0 mmol of barium metal was added to a flask containing 112 mL anydrous benzene, 21 ml isopropanol, and 19.5 ml titanium (IV) isopropoxide and stirred vigorously until the added metal was completely dissolved. The solution exhibited a deep purple color within minutes and gradually became white. Once the metal was dissolved, the solution was placed at 4° C. as the precursor precipitated out of the solution. The precipitated precursors were dried overnight, resulting in a fine white powder, with a formula of BaTi(O-iPr)6.

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Abstract

Nanowires are disclosed which comprise transition metal oxides. The transition metal oxides may include oxides of group II, group III, group IV and lanthanide metals. Also disclosed are methods for making nanowires which comprise injecting decomposition agents into a solution comprising solvents and metallic alkoxide or metallic salt precursors.

Description

BACKGROUND OF THE INVENTION Bulk transition metal oxides that exhibit ferroelectric, piezoelectric, converse piezoelectric, pyroelectric, magnetoresistive, and high-permittivity dielectric properties have been widely used in industry to fabricate various memory devices, ferroelectric capacitors, electromechanical actuators, resonators, sensors, optical switches and waveguides. For example, these transition metal oxides may be used in non-volatile ferroelectric random-access memory (NVFRAM) devices. The basis of NVRAM devices may be the ferroelectric property of the material. Ferroelectric properties of a material include the spontaneous permanent dipole moment exhibited by the material that can be reoriented by external electric field. NVFRAM devices use non-volatile ferroelectric polarization in lieu of field-effect gates and modulate the conductance of the doped semiconductor materials. Nonvolatile FRAMs may be used in consumer electronics, such as smart cards, and may be used as...

Claims

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Application Information

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IPC IPC(8): B82B1/00C01G23/00C01G25/00C01G45/00C01G45/12H01L41/09H01L41/18H03H9/17
CPCB82Y30/00H01L41/1136C01G23/006C01G25/00C01G25/006C01G45/1264C01P2002/52C01P2002/54C01P2002/72C01P2004/03C01P2004/04C01P2004/12C01P2004/16C01P2004/50C01P2004/64C01P2006/40C04B35/62231C04B35/6225C04B35/62259C04B35/6264C04B2235/3208C04B2235/3213C04B2235/3215C04B2235/3227C04B2235/3232C04B2235/3244C04B2235/3262C04B2235/3296C04B2235/441C04B2235/449C04B2235/526C04B2235/5264H01L41/18H03H9/176H03H2009/02165H03H2009/241H01L41/082H01L41/0825H01L41/0933H01L41/094H01L41/0966C01G23/003H10N30/2042H10N30/306H10N30/85H10N30/702B82B1/00B82B3/00
Inventor PARK, HONGKUNLIEBER, CHARLES M.URBAN, JEFFREYGU, OIANYUN, WAN SOO
Owner PRESIDENT & FELLOWS OF HARVARD COLLEGE
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