A review of elastic properties of high-Tc superconductors and some related Cp results

First a brief survey is given of what can be learned about important superconducting and normal-state properties by ultrasonic and other elastic measurements. Some of the characteristic elastic properties of the La
2−x
(Ba, Sr)
x
CuO
4
and YBa
2
Cu
3
O
7
systems are reviewed. In the La-based family it is shown how the elastic observations are closely related to structural and soft-mode properties. The physics of YBa
2
Cu
3
O
7
is shown to be more complex. Finally, our recent results on the fluctuation contribution to the specific heat near T
c
in YBa
2
Cu
3
O
7
are discussed.