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A Type 2 Layered Cuprate
Type 2 Superconductors

     Except for the elements vanadium, technetium and niobium, the Type 2 category of superconductors is comprised of metallic compounds and alloys. The recently-discovered superconducting "perovskites" (metal-oxide ceramics that normally have a ratio of 2 metal atoms to every 3 oxygen atoms) belong to this Type 2 group. They achieve higher Tc's than Type 1 superconductors by a mechanism that is still not completely understood. Conventional wisdom holds that it relates to the planar layering within the crystalline structure (see above graphic). Although, other recent research suggests the holes of hypocharged oxygen in the charge reservoirs are responsible. (Holes are positively-charged vacancies within the lattice.) The superconducting cuprates (copper-oxides) have achieved astonishingly high Tc's when you consider that by 1985 known Tc's had only reached 23 Kelvin. To date, the highest Tc attained at ambient pressure for a material that will form stoichiometrically (by formula) has been 138 K. And the highest Tc overall is 77 C for a material which does not form stoichiometrically (see below list). One theory predicts an upper limit for the layered cuprates (Vladimir Kresin, Phys. Reports 288, 347 - 1997). Others assert there is no limit. Either way, it is almost certain that other, more-synergistic compounds still await discovery among the high-temperature superconductors.

     The first superconducting Type 2 compound, an alloy of lead and bismuth, was fabricated in 1930 by W. de Haas and J. Voogd. But, was not recognized as such until later, after the Meissner effect had been discovered. This new category of superconductors was identified by L.V. Shubnikov at the Kharkov Institute of Science and Technology in the Ukraine in 1936(1) when he found two distinct critical magnetic fields (known as Hc1 and Hc2) in PbTl2. The first of the oxide superconductors was created in 1973 by DuPont researcher Art Sleight when Ba(Pb,Bi)O3 was found to have a Tc of 13K. The superconducting oxocuprates followed in 1986.

     Type 2 superconductors - also known as the "hard" superconductors - differ from Type 1 in that their transition from a normal to a superconducting state is gradual across a region of "mixed state" behavior. Since a Type 2 will allow some penetration by an external magnetic field into its surface, this creates some rather novel mesoscopic phenomena like superconducting "stripes" and "flux-lattice vortices". While there are far too many to list in totality, some of the more interesting Type 2 superconductors are listed below by similarity and with descending Tc's. Where available, the lattice structure of the system is also noted.



Tl7Sn2Ba2MnCu10O20+
     (As an H212 structure)


Tl7Sn2Ba2TiCu10O20+
     (As an H212 structure)


Tl6Sn2Ba2TiCu9O18+
     (As an F212 structure)


Tl7Sn2Ba2SiCu10O20+
     (As an H212 structure)


Tl6Ba4SiCu9O18+
     (As an F212 structure)


Tl5Ba4SiCu8O16+
     (As a D212 structure)


(Tl5Sn2)Ba2SiCu8O16+
     (As a D212 structure)


(Tl5Pb2)Ba2SiCu8O16+
     (As a D212 structure)


(Tl5Pb2)Ba2Si2.5Cu8.5O17+
     (As a D223 structure)


(Tl5Pb2)Ba2Mg2.5Cu8.5O17+
     (As a D223 structure)


(Tl5Pb2)Ba2Mg2Cu9O18+
     (As a D223 structure)


(Tl5Pb2)Ba2MgCu10O20+
     (As a D223 structure)


(Tl4Pb)Ba2MgCu8O13+
     (As a 9223 structure)


(Tl4Ba)Ba2MgCu8O13+
     (As a 9223 structure)


(Tl4Ba)Ba2Mg2Cu7O13+
     (As a 9223 structure)


(Tl4Ba)Ba2Ca2Cu7O13+
     (As a 9223 structure)


(Tl4Ba)Ba4Ca2Cu10Oy
     (As a 9212/2212C intergrowth.)


Tl5Ba4Ca2Cu10Oy
     (As a 9212/2212C intergrowth.)


(Sn5In)Ba4Ca2Cu11Oy
     (As a B212/2212C intergrowth.)


(Sn5In)Ba4Ca2Cu10Oy
     (As a B212/1212C intergrowth.)


Sn6Ba4Ca2Cu10Oy
     (As a B212/1212C intergrowth.)


(Sn1.0Pb0.5In0.5)Ba4Tm6Cu8O22+
     (As a 1256/1212 intergrowth.)


(Sn1.0Pb0.5In0.5)Ba4Tm5Cu7O20+
     (As a 1245/1212 intergrowth.)


(Sn1.0Pb0.5In0.5)Ba4Tm4Cu6O18+
     (As a 1234/1212 intergrowth)


Sn3Ba4Ca2Cu7Oy
     (As a 5212/1212C intergrowth.)

 +77 C 


 +65 C 


 +56 C 


 +53 C 


 +48 C 


 +44 C 


 +42 C 


 +38 C 


 +35 C 


 +30 C 


 +28 C 


 +18 C 


 +3 C 


 ~265 K 


 ~258 K 


 ~254 K 


 ~242 K 


 ~233 K 


 ~218 K 


 ~212 K 


 ~200 K 


 ~195 K 


 ~185 K  


 ~163 K  


 ~160 K  



(Hg0.8Tl0.2)Ba2Ca2Cu3O8.33
HgBa2Ca2Cu3O8
HgBa2Ca3Cu4O10+ 
HgBa2(Ca1-xSrx)Cu2O6+
HgBa2CuO4

   138 K*
 133-135 K
 125-126 K
 123-125 K
   94-98 K


 Lattice: TET

* Note: As a result of a topological "defect", Hg will also go into the Cu atomic sites. Thus, the volume fraction of the intended structure type is typically just 15 - 30% of the bulk.


Tl2Ba2Ca2Cu3O10
(Tl1.6Hg0.4)Ba2Ca2Cu3O10+
TlBa2Ca2Cu3O9+
(TlSn)Ba4TmCaCu4O14+
(Tl0.5Pb0.5)Sr2Ca2Cu3O9
Tl2Ba2CaCu2O6
TlBa2Ca3Cu4O11
(Tl0.5Pb0.5Sn)Ba4Tm3Cu5O16+
TlBa2CaCu2O7+
Tl2Ba2CuO6
TlSnBa4Y2Cu4Ox

  127-128 K
    126 K
    123 K
  ~121 K   (Superconductors.ORG - 2005)
  118-120 K
    118 K
    112 K
    105 K   (Superconductors.ORG - 2011)
    103 K
     95 K
     86 K    (Superconductors.ORG - 2007)
 

 Lattice: TET


Sn4Ba4(Tm2Ca)Cu7Ox
Sn2Ba2(Tm0.5Ca0.5)Cu3O8+
SnInBa4Tm3Cu5Ox
Sn3Ba4Tm3Cu6Ox
Sn3Ba8Ca4Cu11Ox
SnBa4Y2Cu5Ox
Sn4Ba4Tm2YCu7Ox
Sn4Ba4TmCaCu4Ox
Sn4Ba4Tm3Cu7Ox
Sn2Ba2(Y0.5Tm0.5)Cu3O8+
Sn3Ba4Y2Cu5Ox
SnInBa4Tm4Cu6Ox
Sn2Ba2(Sr0.5Y0.5)Cu3O8
Sn4Ba4Y3Cu7Ox
 ~127 K    (TmTm-Ca structure only)
 ~115 K   (Superconductors.ORG - 2005)
 ~113 K   (Superconductors.ORG - 2005)
   109 K   (Superconductors.ORG - 2007)
   109 K   (One-of-a-Kind Resonant - 2006)
   107 K    (Superconductors.ORG - 2007)
  ~104 K   (First Hi-Tc Reentrant - 2007)
  ~100 K   (Superconductors.ORG - 2007)
  ~98 K   (Superconductors.ORG - 2006)
  ~96 K   (Superconductors.ORG - 2007)
  ~91 K   (Superconductors.ORG - 2006)
    87 K    (Superconductors.ORG - 2005)
    86 K     (Aleksandrov, et al - 1989)
  ~80 K    (Superconductors.ORG - 2005)


Bi1.6Pb0.6Sr2Ca2Sb0.1Cu3Oy
Bi2Sr2Ca2Cu3O10***
Bi2Sr2CaCu2O9***
Bi2Sr2(Ca0.8Y0.2)Cu2O8
Bi2Sr2CaCu2O8
BiSnBa4TmCaCu4O14
   115 K  (thick film on MgO substrate)
   110 K 
   110 K 
    95-96K
    91-92K
    83K  (Superconductors.ORG - 2012)

 Lattice: ORTH

*** Though not always listed as a component, a small amount of Lead (x=.2-.26) is often used with Bismuth compounds to help facilitate a higher-Tc crystalline phase.


CaSrCu2O4
YSrCa2Cu4O8+
(Ba,Sr)CuO2
BaSr2CaCu4O8+
(La,Sr)CuO2
 110 K
 101 K    (Superconductors.ORG - 2007)
   90 K
   90 K     (Superconductors.ORG - 2007)
   42 K

*** The above 5 compounds are all "infinite layer".


Pb3Sr4Ca3Cu6Ox
Pb3Sr4Ca2Cu5O15+
(Pb1.5Sn1.5)Sr4Ca2Cu5O15+
Pb2Sr2(Ca, Y)Cu3O8
 106 K    (Superconductors.ORG - 2007)
 101 K    (Superconductors.ORG - 2005)
 ~95 K    (Superconductors.ORG - 2006)
   70 K   (Cava, et al - 1989)


AuBa2Ca3Cu4O11 
AuBa2(Y, Ca)Cu2O
AuBa2Ca2Cu3O
  99 K    (Kopnin, et al - 2001)
  82 K
  30 K

 Lattice: ORTH




TaBa7Cu8Ox   (B212C structure)
TeBa7Cu8Ox   (B212C structure)
YBa3Cu4Ox   (9223C structure)
YCaBa3Cu5O11+
(Y0.5Lu0.5)Ba2Cu3O7
(Y0.5Tm0.5)Ba2Cu3O7
Y3Ba5Cu8O18+
Y2Ba5Cu8O17+
Y3CaBa4Cu8O18+
TeBa3Cu4Ox
(Y0.5Gd0.5)Ba2Cu3O7
Y2CaBa4Cu7O16
Y3Ba4Cu7O16
Y2Ba5Cu7Ox
NdBa2Cu3O7
Y2Ba4Cu7O15
GdBa2Cu3O7
YBa2Cu3O7
TmBa2Cu3O7
YbBa2Cu3O7
YSr2Cu3O7

Lattice: TET

 255 K   (Superconductors.ORG - 2013)
 253 K   (Superconductors.ORG - 2014)
 177 K   (Superconductors.ORG - 2009)
 107 K  (Superconductors.ORG - 2010)
 106 K    (Superconductors.ORG - 2005)
 104 K    (Superconductors.ORG - 2005)
 104 K    (Superconductors.ORG - 2008)
 104 K    (Superconductors.ORG - 2012)
  99 K    (Superconductors.ORG - 2010)
  98 K    (Superconductors.ORG - 2013)
  97 K    (Superconductors.ORG - 2005)
  96 K   (Superconductors.ORG - 2006)
  96 K    (Superconductors.ORG - 2005)
  96 K    (Superconductors.ORG - 2008)
  96 K
  95 K
  94 K
  92 K   (See above graphic)
  90 K
  89 K
  62 K

 Comment: "1-2-3" superconductors actually have the 1212C structure. Thus, the formula for YBCO could be written CuBa2YCu2O7.


GaSr2(Ca0.5Tm0.5)Cu2O7
Ga2Sr4Y2CaCu5Ox
Ga2Sr4Tm2CaCu5Ox
La2Ba2CaCu5O9+ 
(Sr,Ca)5Cu4O10
GaSr2(Ca, Y)Cu2O7
(In0.3Pb0.7)Sr2(Ca0.8Y0.2)Cu2Ox
(La,Sr,Ca)3Cu2O6
La2CaCu2O6+
(Eu,Ce)2(Ba,Eu)2Cu3O10+
(La1.85Sr0.15)CuO4
SrNdCuO****
(La,Ba)2CuO4
(Nd,Sr,Ce)2CuO4
Pb2(Sr,La)2Cu2O6
(La1.85Ba.15)CuO4

 99 K    (Superconductors.ORG - 2006)

 85 K    (Superconductors.ORG - 2006)
 81 K    (Superconductors.ORG - 2006)
 79 K   (Saurashtra Univ., Rajkot, India - 2002)
 70 K
 70 K
 60 K
 58 K
 45 K
 43 K
 40 K
 40 K
 35-38 K
 35 K
 32 K
 30 K   (First HTS ceramic SC discovered - 1986)

**** First ceramic superconductor discovered without a non-superconducting oxide layer.

Comment: All of the above are copper perovskites, even though their metal-to-oxygen ratios are not exactly 2-to-3. The best performers are those compounds that contain one or more of the electron-emitters BaO, SrO or CaO, along with a Period 6 heavy metal like Mercury, Thallium, Lead, Bismuth, or Gold.


 GdFeAsO1-x
 (Ca,Sr,Ba)Fe2As2
 LiFeAs

  53.5 K  (Highest Tc iron-based compound)
   38 K   
   18 K   

Comment: The above are members of the newly discovered iron pnictide family.



 MgB2
 Ba0.6K0.4BiO3

  39 K  (Highest Tc Non-Fullerene Alloy)
  30 K   (First 4th order phase compound)


 Nb3Ge
 Nb3Si
 Nb3Sn
 Nb3Al
 V3Si
 Ta3Pb
 V3Ga
 Nb3Ga
 V3In
 23.2 K
 19 K
 18.1 K
 18 K
 17.1 K
 17 K
 16.8 K
 14.5 K
 13.9 K

  Lattice: A15

  Comment: Among the binary alloys, these are some of the best performers; combining Group 5B metals in a ratio of 3-to-1 with 4A or 3A elements.


PuCoGa5  18.5 K    (First SC transuranic compound)


NbN  16.1 K

Comment: After NbTi (below) NbN is the most widely used low-temperature superconductor.

Nb0.6Ti0.4
MgCNi3
 9.8 K      (First superconductive wire)
 7-8 K      (First all-metal perovskite superconductor)


C
Nb
Tc
V
 15 K      (as highly-aligned, single-walled nanotubes)
 9.25 K
 7.80 K
 5.40 K

 Lattice: C=Fullerene, Nb=BCC, Tc=HEX, V=BCC

 Comment: These four are the only elemental Type 2 superconductors.

RuSr2(Gd,Eu,Sm)Cu2O8
ErNi2B2C
YbPd2Sn
UGe2
URhGe2
AuIn3
Tc ~58 K   (Ruthenium-oxocuprate)
Tc  10.5 K    (Nickel-Borocarbide)
Tc ~2.5 K  (Heusler compound)
Tc ~1K    (Heavy fermion)
Tc ~1K             ( " )
Tc  50 uK

Comment: The above 6 compounds are all rare ferromagnetic superconductors.


Sr.08WO3
Tl.30WO3
Rb.27-.29WO3
  2-4 K     (Tungsten-bronze)
2.0-2.14 K          (")
  1.98 K               (")

 Lattice: TET


SrTiO3   0.35 K 

 Comment: This is the first oxide insulator found to be superconductive.

(1.)  "History of Physics Research in Ukraine", by Oleksandr Bakai and Yurij Raniuk, Kharkov Institute of Science and Technology, 1993.

Author's Comment:  The Tc's noted on this page were obtained from a variety of sources including, but not limited to, the CRC Handbook of Chemistry and Physics, the N.I.S.T. database, Physica C, industry news sources, and various private researchers. In cases where there was a discrepancy between sources, the higher Tc or a range of Tc's has been listed.

[Last page rev: Jan. 2013]