Session B25 - M/"{o}ssbauer and Perturbed Angular Correlation Spectroscopies.
MIXED session, Monday morning, March 18
Room 123, America's Center

[B25.02] Point Defect Formation Enthalpies Measured at High Temperature by PAC.

In our laboratory we have observed vacancies quenched in highly-ordered intermetallic compounds such as NiAl, CoAl and PdIn by the quadrupole interactions induced at nuclei of perturbed-angular-correlation (PAC) probe atoms. Precise activation enthalpies and entropies of formation of the vacancy defects have been determined from observed vacancy site fractions using a methodology developed by us.(Jiawen Fan and Gary S. Collins, unpublished.) The methodology allows for local motion and binding of vacancies with impurity probe atoms during the quench. To test the validity of the methodology and of the results obtained for quenched samples, we are beginning complementary measurements of vacancy site fractions at high temperature. For this purpose, we built a new PAC oven that in principle is able to reach temperatures above 1500 \(^0C\) using electron-beam heating. First measurements are just now being made using the oven and results will be reported at the meeting, along with the oven's design and performance.