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Alkaline earth metal titanate crystal laminate

Foreign code F210010323
File No. J1023-03WO
Posted date Feb 1, 2021
Country United States of America
Application number 201816647333
Gazette No. 20200346941
Date of filing Sep 14, 2018
Gazette Date Nov 5, 2020
International application number JP2018034156
International publication number WO2019054474
Date of international filing Sep 14, 2018
Date of international publication Mar 21, 2019
Priority data
  • P2017-177321 (Sep 15, 2017) JP
  • 2018JP34156 (Sep 14, 2018) WO
Title Alkaline earth metal titanate crystal laminate
Abstract There are provided a new type of crystal laminate of an alkaline earth metal titanate having improved catalytic activity, and a method for producing the same. The crystal laminate is provided having a crystal of the alkaline earth metal titanate as a constitutional unit, wherein the crystal being the constitutional unit is a cubic crystal, a tetragonal crystal or an orthorhombic crystal; the crystal being the constitutional unit has a primary particle diameter of 500 nm or less; and the crystal is layered with an orientation in a {100} plane direction thereof.
Outline of related art and contending technology BACKGROUND ART
Alkaline earth metal titanates such as strontium titanate and barium titanate have photocatalytic activity and high dielectricity, and are used for photohydrolysis, ceramic capacitors, piezoelectric elements and the like. Nanoparticles of metal titanates, however, are liable to randomly aggregate, and the decrease in surface area, the interfacial mismatch and the like caused thereby pose the following problem: the decrease in photocatalytic activity and light energy conversion efficiency.
As means for solving the above problem, with regard to metal oxide nanoparticles, reported were means in which metal oxide nanoparticles are made into a metal oxide mesocrystal, which is a superstructure made by self-organization of the metal oxide nanoparticles (Non Patent Literatures 1 and 2). The present inventor has further studied in order to conveniently obtain a mesocrystal of a metal oxide represented by titanium oxide, and has then found that by calcining using an aqueous solution containing a metal oxide precursor, an ammonia salt and water, or a metal oxide precursor, an ammonia salt, a surfactant and water, a metal oxide mesocrystal having a large size and a large specific surface area can be obtained (Patent Literatures 1 and 2). It has also been found that a mesocrystal of a composite oxide containing two or more metal species can also be obtained (Patent Literature 2).
Scope of claims [claim1]
1. A crystal laminate, comprising:
a crystal of an alkaline earth metal titanate as a constitutional unit, wherein:
the crystal is a cubic crystal, a tetragonal crystal or an orthorhombic crystal;
the crystal has a primary particle diameter of 500 nm or less; and
the crystal is layered with an orientation in a {100} plane direction thereof.

[claim2]
2. The crystal laminate according to claim 1, wherein the crystal laminate has an average width of 1 μm or more.

[claim3]
3. The crystal laminate according to claim 1, wherein the crystal laminate has an average thickness of 50 nm or more.

[claim4]
4. The crystal laminate according to claim 1, wherein the crystal present on a surface of the crystal laminate has a primary particle diameter more than a primary particle diameter of the crystal present in an interior of the crystal laminate.

[claim5]
5. The crystal laminate according to claim 1, wherein the crystal laminate has a specific surface area of 10 m2/g or more.

[claim6]
6. A structure having an alkaline earth metal titanate crystal nanoparticle on a surface of the crystal laminate according to claim 1, wherein
a crystal orientation of the alkaline earth metal titanate crystal nanoparticle is in the same direction as that of the crystal laminate.

[claim7]
7. The structure according to claim 6, wherein the alkaline earth metal titanate crystal nanoparticle has a primary particle diameter of twice or more a primary particle diameter of the crystal present on the surface of the crystal laminate.

[claim8]
8. The structure according to claim 6, wherein the alkaline earth metal titanate crystal nanoparticle has a primary particle diameter of 50 nm or more.

[claim9]
9. A method for producing a crystal laminate of an alkaline earth metal titanate, the method comprising:
subjecting a titanium oxide mesocrystal having a titanium oxide nanoparticle orderly layered therein and an alkaline earth metal atom source to a hydrothermal reaction.
  • Inventor, and Inventor/Applicant
  • TACHIKAWA TAKASHI
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
IPC(International Patent Classification)
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