Table:
text: High-temperature superconductivity
Bi-, Tl- and Hg-based high-  c  superconductors
Critical temperature (T c ), crystal structure and lattice constants of some high-T c superconductors
Formula Notation T_c_K No_of_Cu_O_planes_in_unit_cell Crystal_structure
YBa 2 Cu 3 O 7 123 92 2 Orthorhombic
Bi 2 Sr 2 CuO 6 Bi-2201 20 1 Tetragonal
Bi 2 Sr 2 CaCu 2 O 8 Bi-2212 85 2 Tetragonal
Bi 2 Sr 2 Ca 2 Cu 3 O 6 Bi-2223 110 3 Tetragonal
Tl 2 Ba 2 CuO 6 Tl-2201 80 1 Tetragonal
Tl 2 Ba 2 CaCu 2 O 8 Tl-2212 108 2 Tetragonal
Tl 2 Ba 2 Ca 2 Cu 3 O 10 Tl-2223 125 3 Tetragonal
TlBa 2 Ca 3 Cu 4 O 11 Tl-1234 122 4 Tetragonal

Question: How often is the formula for high-temperature superconductivity: tl 2 ba 2 cuo 6 ?

Question: What is the crystal structure of high-temperature superconductivity for the formula yba 2 cu 3 o 7 ?

Question: What is the high-temperature superconductivity number for tc(k) when the notation is tl-2212?