StudentLecture_28 (1)

StudentLecture_28 (1) - This week in CHM 11500 T, Lecture...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
This week in CHM 11500 T, Lecture 28, 12/8/2009 Check out of lab. Remember: Safety goggles Appropriate dress HW due Friday. Final Exam: Tuesday, December 15, 8:00 AM Hall of Music ~60 % cumulative, ~40 % new material Help Session: Sunday, 13 Dec. at 1 to 3 PM in Lilly Hall 1105 Sorry, I forgot to post notes. This set will be posted later today.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Superconducting Ceramics Superconductivity is a phenomenon in which the electrical resistivity of a material drops to zero at some low temperature This is the “ critical temperature ”, written T c Some metals and metal alloys exhibit superconductivity at T c near 0-20 K! (very inconvenient temperatures, require liquid helium , bp 4 K) Some ceramics have T c around 100 K ( much nicer, liquid N 2 , bp 77 K) Complex formulas: YBa 2 Cu 3 O 7 with T c = 92 K 8 demo
Background image of page 2
Superconducting Ceramics Lattice of a YBa 2 Cu 3 O 7 superconductor Ionic solid, difficult to form flexible wires.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
How does electrical conduction happen in solids? Band theory Recall atomic energy levels and orbitals Valence orbitals = outermost orbital with highest n value
Background image of page 4
Band Theory As the number of atoms in a solid increases, the number of available energy levels increases. The number of energy levels from a single type of orbital in a cluster of atoms = the total number available from the individual atoms For Li 2s orbitals; 1 valence electron from each Li atom.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Band Theory As the number of atoms in the group increases, the energy levels get closer and closer make a continuous band. forming an unfilled band. Note the errors, 3 electrons per energy level!
Background image of page 6
Band Theory Other energy levels will give empty bands. For some solids this results in a lower energy filled band (“ valence band ”), and a higher eneregy empty
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/21/2010 for the course CHEM 115 taught by Professor L during the Spring '02 term at Purdue University.

Page1 / 27

StudentLecture_28 (1) - This week in CHM 11500 T, Lecture...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online