Microstrain effect on thermal properties of nanocrystalline Cu

The nanocrystalline (nc) Cu samples with different microstrains but the same grain size were obtained by annealing a magnetron-sputtered ne Cu specimen. Quantitative X-ray diffraction (XRD) measurements show that with an increment of the microstrain from 0.14 to 0.24% the thermal expansion coefficient (TEC) of crystalline lattice increases by about 12%, the static displacement of atom from the equilibrium position (B-S) increases from 0.47 +/- 0.09 to 1.16 +/- 0.15 Angstrom(2), and Debye characteristic temperature (Theta(D)) decreases from 307.1 +/- 3.1 to 279.2 +/- 2.8 K. The microstrain effect on thermal properties in the nc Cu might be attributed to the change in density of grain boundary defects/dislocations. The present investigation demonstrates that the thermal properties of ne materials are determined by not only the grain size but also the microstructure of grain boundaries. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.