Perovskite manganese oxides with strong magnetocaloric effect and uses thereof

Patent metadata

Field	Value
Publication number	US-11670441-B2
Application number	US-201816768173-A
Country	US
Kind code	B2
Filing date	Dec 1, 2018
Priority date	Dec 1, 2017
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

Abstract

In various aspects, methods of making perovskite manganese oxide particles are provided as well as perovskite manganese oxide particles made therefrom. The perovskite manganese oxide particles exhibit a strong magnetocaloric effect, making them well suited for applications in power generation and magnetic refrigeration, especially at or near room temperature. The methods can include forming an aqueous mixture of (i) a low-molecular-weight polymeric polyalcohol gel precursor, (ii) a stoichiometric amount of metal salts or hydrates thereof, wherein the metal salts or hydrates thereof comprise at least a Manganese (Mn), and (iii) a polybasic carboxylic acid; polymerizing the aqueous mixture to form a gel containing perovskite manganese oxide nanoparticles entrapped therein; and calcining the gel to remove at least a portion of organic material in the gel and form the perovskite manganese oxide particles. Method and systems are also provided for power generation and magnetic refrigeration using the perovskite manganese oxide particles.

First claim

I claim:

1. A method of making perovskite manganese oxide particles having a strong magnetocaloric effect, the method comprising:
forming an aqueous mixture comprising (i) a low-molecular-weight polymeric polyalcohol gel precursor, (ii) a stoichiometric amount of metal salts or hydrates thereof, wherein the metal salts or hydrates thereof comprise at least a Manganese (Mn), and (iii) a polybasic carboxylic acid;
polymerizing the aqueous mixture to form a gel comprising perovskite manganese oxide nanoparticles entrapped therein; and
calcining the gel to remove at least a portion of organic material in the gel and form the perovskite manganese oxide particles.

2. The method according to claim 1 , wherein the low-molecular-weight polymeric polyalcohol gel precursor comprises a low-molecular-weight polyethylene glycol.

3. The method according to claim 1 , wherein the low-molecular-weight polymeric polyalcohol gel precursor comprises a low-molecular-weight polyvinyl alcohol.

4. The method according to claim 1 , wherein the metal salts or hydrates thereof comprise a metal hydroxide, a metal alkoxide, a metal acetate, a metal chloride, a metal citrate, a metal nitrate, or a combination thereof.

5. The method according to claim 1 , wherein the metal salts or hydrates thereof further comprise a metal selected from the group consisting of Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Gadolinium (Gd), Calcium (Ca), Strontium (Sr), Barium (Ba), and a combination thereof.

6. The method according to claim 1 , wherein the perovskite manganese oxide particles comprise a doped manganese oxide;
wherein the metal salts or hydrates thereof further comprise a trivalent rare-earth metal and a divalent metal; and
wherein a molar ratio of a first total amount of Mn to a second total amount of trivalent rare-earth metal and divalent metal in the aqueous mixture is about 1.

7. The method according to claims 1 , wherein the perovskite manganese oxide particles comprise La 1-x Ca x MnO 3 , wherein x is about 0.1 to 0.5; and
wherein the metal salts or hydrates thereof further comprise La and Ca.

8. The method according to claim 1 , wherein the perovskite manganese oxide particles comprise La 1-x Sr x MnO 3 , wherein x is about 0.1 to 0.5; and
wherein the metal salts or hydrates thereof further comprise La and Sr.

9. The method according to claim 1 , wherein the polybasic carboxylic acid is selected from the group consisting of citric acid, glycolic acid, tartaric acid, maleic acid, hydroxymaleic acid, hydroxytartaric acid, malonic acid, malic acid, lactic acid, tartronic acid, gluconic acid, saccharic acid, glucuronic acid, mucic acid, mannosaccharic acid, and a combination thereof.

10. The method according to claim 1 , wherein the low-molecular-weight polymeric polyalcohol gel precursor is present in the aqueous mixture at a weight ratio (w/w) of the low-molecular-weight polymeric polyalcohol gel precursor to the metal of about 1:10.

11. The method according to claims 1 , wherein each of the metal salts or the hydrate thereof is present in the aqueous mixture at a concentration of about 0.1 M to 1.0 M.

12. The method according to claim 1 , wherein the polybasic carboxylic acid is present in the aqueous mixture at a weight ratio (w/w) of the polybasic carboxylic acid to the metal of about 1:10.

13. The method according to claim 1 , wherein the polymerizing step comprises one or both of (i) lowering the pH of the aqueous mixture by the addition of an acid and (ii) heating the aqueous mixture to a first elevated temperature for a first period of time to form the gel.

14. The method according to claim 13 , wherein the first elevated temperature is about 50° C. to 100° C., about 60° C. to 90° C., or about 65° C. to 80° C.; and
wherein the first period of time is about 3 hours to 10 hours or about 4 hours to 8 hours.

15. The method according to claim 1 , wherein the calcining step comprises heating the gel to a second elevated temperature for a second period of time to remove the portion of the organic material.

16. The method according to claim 15 , wherein the portion is substantially all of the organic material.

17. The method according to claim 15 , wherein the second elevated temperature is selected from the group consisting of about 400° C. to 1200° C., about 500° C. to 1100° C., or about 600° C. to 1000° C.; and
wherein the second period of time is about 10 hours.

18. A plurality of perovskite manganese oxide particles produced by the method according to claim 1 .

19. The plurality of particles according to claim 18 , wherein the plurality of particles has a particle-like morphology.

20. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide comprises a metal selected from the group consisting of Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Calcium (Ca), Strontium (Sr), Barium (Ba), and a combination thereof.

21. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles comprise a doped manganese oxide comprising a trivalent rare-earth metal and a divalent metal; and
wherein a molar ratio of a first total amount of Mn to a second total amount of trivalent rare-earth metal and divalent metal in the aqueous perovskite manganese oxide particles is about 1.

22. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles comprise La 1-x Ca x MnO 3 , wherein x is about 0.1 to 0.5.

23. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles comprise La 1-x Sr x MnO 3 , wherein x is about 0.1 to 0.5.

24. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles have a relative cooling power (RCP) of about 600 J Kg −1 to 1600 J Kg −1 at 278 K for a field change of 0-3 T.

25. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles have a magnetic entropy (−ΔS M ) of about 10 Jkg −1 K −1 to about 30 Jkg −1 K −1 or about 15 Jkg −1 K −1 to about 30 Jkg −1 K − 1 when measured at 278 K for a field change of 0-3 T.

26. The plurality of particles according to claim 18 , wherein the perovskite manganese oxide particles comprise La 1-x Ca x MnO 3 or La 1-x Sr x MnO 3 , wherein x is about 0.1 to 0.5;
wherein the metal salts or hydrates thereof further comprise La and Ca or Sr;
wherein the low-molecular-weight polymeric polyalcohol gel precursor comprises a low-molecular-weight polyethylene glycol having a number average molecular weight of about 400 Daltons to about 1000 Daltons;
wherein the plurality of particles has an average crystallite size of about 25 nm to 75 nm when measured according to the Sherrer equation using the highest intensity peak in the X-ray diffraction of the plurality of particles;
wherein the plurality of particles has an average particle size of about 25 nm to 125 nm when measured by transmission electron microscopy;
wherein the perovskite manganese oxide particles have a relative cooling power (RCP) of about 600 J Kg-1 to 1600 J Kg -1 and a magnetic entropy (−ΔS M ) of about 15 Jkg −1 K −1 to about 30 Jkg −1 K − 1 when measured at 278 K for a field change of 0-3 T.

27. A magnetic refrigeration device comprising a refrigerant material comprising a plurality of perovskite manganese oxide particles according to claim

Assignees

• Univ Virginia Commonwealth

Inventors

• Carpenter Everett E

Classifications

• H01F1/017 Primary

  Compounds · CPC title

• F25B21/00

  Machines, plants or systems, using electric or magnetic effects · CPC title

• F25B2321/002

  by using magneto-caloric effects · CPC title

• Y02B30/00

  Energy efficient heating, ventilation or air conditioning [HVAC] · CPC title

• H01F1/012 Primary

  adapted for magnetic entropy change by magnetocaloric effect, e.g. used as magnetic refrigerating material (refrigeration systems using magnetic effects F25B21/00) · CPC title