Voltage tunability of thermal conductivity in ferroelectric materials

Patent metadata

Field	Value
Publication number	US-9255347-B2
Application number	US-201414546147-A
Country	US
Kind code	B2
Filing date	Nov 18, 2014
Priority date	Nov 22, 2013
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

First claim

We claim:

1. A method to control thermal conductivity in a ferroelectric material, comprising:
growing an epitaxial or polycrystalline film of ferroelectric material on a substrate; and
applying a sufficient electric field across the film to modify the domain structure in the film, thereby altering the thermal conductivity of the film.

2. The method of claim 1 , wherein the spacing of the domain walls of the domain structure is less than or comparable to the mean free path of phonons at a temperature of interest.

3. The method of claim 2 , wherein the temperature of interest is between 30K and 600K.

4. The method of claim 1 , wherein the thickness of the film is less than 5 micron.

5. The method of claim 1 , wherein the ferroelectric material comprises a perovskite ferroelectric.

6. The method of claim 5 , wherein the perovskite ferroelectric comprises a rhombohedrally symmetric perovskite ferroelectric, a tetragonally symmetric perovskite ferroelectric, or an orthorhombic perovskite ferroelectric.

7. The method of claim 5 , wherein the perovskite ferroelectric comprises (Pb,La)(Zr,Ti,Nb)O 3 , BaTiO 3 , BiFeO 3 , or (Bi,RE)FeO 3 , where RE is a lanthanide metal cation.

8. The method of claim 1 , wherein the ferroelectric material comprises (Ba,Sr)TiO 3 , (Ba,Ca,Sr)TiO 3 , (Ba,Sr)(Ti,Zr)O 3 , or (Ba,Sr,Ca,Pb)(Ti,Zr,Hf,Sn)O 3 .

9. The method of claim 1 , wherein the ferroelectric material comprises a relaxor ferroelectric.

10. The method of claim 1 , wherein the ferroelectric material comprises a ferroelastic material.

11. The method of claim 1 , wherein the ferroelectric material comprises a paraelectric material.

12. The method of claim 1 , wherein the substrate comprises a single crystal substrate.

13. The method of claim 12 , wherein the single crystal substrate has a lattice constant that is different than the film, thereby imposing strain on the film.

14. The method of claim 13 , wherein the ferroelectric material comprises BiFeO 3 and the single crystal substrate comprises NdGaO 3 , SrTiO 3 , or DyScO 3 , thereby imposing a compressive strain on the BiFeO 3 film.

15. The method of claim 13 , wherein the ferroelectric material comprises BiFeO 3 and the single crystal substrate comprises GdScO 3 or KTaO 3 , thereby imposing a tensile strain on the BiFeO 3 film.

16. The method of claim 13 , wherein the ferroelectric material comprises Pb(Zr,Ti)O 3 and the single crystal substrate comprises non-perovskite spinel (MgAl 2 O 4 ) or rocksalt (MgO), thereby imposing a tensile strain on the Pb(Zr,Ti)O 3 film.

17. The method of claim 1 , wherein the substrate comprises a vicinal substrate.

18. The method of claim 17 , wherein the ferroelectric material comprises BiFeO 3 and the vicinal substrate comprises (001)-oriented SrTiO 3 , thereby imposing a compressive strain on the BiFeO 3 film.

19. The method of claim 1 , wherein the substrate comprises metallized silicon.

20. The method of claim 1 , further comprising depositing an electrode on the film to enable applying the electric field across the film.

21. The method of claim 20 , wherein the electrode comprises an epitaxial conductive oxide electrode.

22. The method of claim 21 , wherein the epitaxial conductive oxide electrode comprises SrRuO 3 or (La,Sr)MnO 3 .

23. The method of claim 20 , wherein the electrode comprises a metal.

24. The method of claim 1 , further comprising depositing a sacrificial layer on the substrate prior to growing the film and etching away the sacrificial layer to remove the substrate prior to applying the electric field across the film.

25. The method of claim 24 , wherein the sacrificial layer comprises MgO or ZnO.

26. The method of claim 1 , wherein the substrate is mechanically and/or chemically thinned prior to applying the electric field across the film.

Assignees

• Sandia Corp
• Hopkins Patrick E

Inventors

• Ihlefeld Jon
• Hopkins Patrick Edward

Classifications

• C30B29/32 Primary

  Titanates; Germanates; Molybdates; Tungstates · CPC title

• B81C1/00476

  removing a sacrificial layer (B81C1/00912 takes precedence) · CPC title

• H01B1/00

  Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors · CPC title

• C09K13/00

  Etching, surface-brightening or pickling compositions (for glass C03C15/00, {C03C25/66; for mortars, concrete, artificial or natural stone or ceramics C04B41/5338}; for metallic material C23F, C23G1/00, C25F1/00; {for semi-conductors H10P52/40}) · CPC title

• B24B37/042

  operating processes therefor · CPC title