Multifferoic R-type hexaferrite, a composite and an article comprising the R-type hexaferrite, and a method of making the same
In an aspect, an R-type ferrite has the formula: Me′ 3 Me 2 TiFe 12 O 25 , wherein Me′ is at least one of Ba 2+ or Sr 2+ and Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ . In another aspect, a composite or an article comprises the R-type ferrite. In yet another aspect, a method of making a R-type ferrite comprises milling ferrite precursor compounds comprising oxides of at least Fe, Ti, Me, and Me′, to form an oxide mixture; wherein Me′ comprises at least one of Ba 2+ or Sr 2+ ; Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ ; and calcining the oxide mixture in an oxygen or air atmosphere to form the R-type ferrite.
1 . A ferrite, having the formula:
Me′ 3 Me 2 TiFe 12 O 25
and comprising a Me′TiO 3 layer between two Me′MeFe 6 O 11 layers,
wherein Me′ is at least one of Ba 2+ or Sr 2+ and Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ .
2 . The ferrite of claim 1 , wherein the Me′ comprises Ba 2+ .
3 . The ferrite of claim 1 , wherein the ferrite has the formula:
Ba 3 Co 2-x Me″ x TiFe 12 O 25
wherein Me″ is at least one of Mg 2+ , Cu 2+ , or Zn 2+ and x is 0 to 2.
4 . The ferrite of claim 1 , wherein the ferrite is multiferroic showing ferrimagnetic and ferroelectric ordering at greater than or equal to 23° C.
5 . The ferrite of claim 1 , wherein the ferrite has a permeability of greater than or equal to 2 at a frequency of 1 to 3 gigahertz.
6 . The ferrite of claim 1 , wherein the ferrite has a magnetic loss tangent tan δ μ of less than or equal to 0.8 at a frequency of 1 to 3 gigahertz.
7 . The ferrite of claim 1 , wherein the ferrite has a Snoek product of greater than or equal to 10 gigahertz over the frequency range of 1 to 3 gigahertz.
8 . A composite comprising a polymer and the ferrite of claim 1 .
9 . The composite of claim 8 , wherein the polymer comprises at least one of a fluoropolymer or a polyolefin.
10 . An article comprising the ferrite of claim 1 .
11 . The article of claim 10 , wherein the article is an antenna, a filter, an inductor, a circulator, or an EMI suppressor.
12 . A method of making the ferrite of claim 1 , the method comprising:
milling ferrite precursor compounds comprising oxides of at least Fe, Ti, Me, and Me′, to form an oxide mixture; wherein Me′ comprises at least one of Ba 2+ or Sr 2+ ; Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ ; and
calcining the oxide mixture in an oxygen or air atmosphere to form the ferrite.
13 . The method of claim 12 , wherein
the milling occurs for greater than or equal to 4 hours; or at a mixing speed of greater than or equal to 300 revolutions per minute;
the calcining the calcined ferrite occurs at a calcining temperature of 800 to 1,300° C. for a calcining time of 0.5 to 20 hours; or
a combination thereof.
14 . The method of claim 12 , further comprising
post-annealing the ferrite in an oxygen or air atmosphere after the high energy milling; wherein the post-annealing occurs at an annealing temperature of 900 to 1,275° C. for an annealing time of 1 to 20 hours;
forming a composite comprising the ferrite and a polymer; or
a combination thereof.
15 . A hexagonal or crystalline structure ferrite having the formula:
Me′ 3 Me 2 TiFe 12 O 25
wherein Me′ is at least one of Ba 2+ or Sr 2+ and Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ .
16 . A polycrystalline structure ferrite having the formula:
Me′ 3 Me 2 TiFe 12 O 25
wherein Me′ is at least one of Ba 2+ or Sr 2+ and Me is at least one of Co 2+ , Mg 2+ , Cu 2+ , or Zn 2+ .
17 . The hexagonal or crystalline structure ferrite of claim 15 , wherein the hexagonal or crystalline structure ferrite is a hexagonal structure ferrite.
18 . The hexagonal or crystalline structure ferrite of claim 15 , wherein the hexagonal or crystalline structure ferrite is a crystalline structure ferrite.
19 . The method of claim 16 , wherein the crystalline structure of the polycrystalline structure ferrite has an average grain size of 1 to 100 micrometers.
20 . The method of claim 19 , wherein the crystalline structure has an average grain size of 5 to 50 micrometers.