Microstrain effect on thermal properties of nanocrystalline Cu Original Research Article

The nanocrystalline (nc) Cu samples with different microstrains but the same grain size were obtained by annealing a magnetron-sputtered nc 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 (BS) increases from 0.47±0.09 to 1.16±0.15 Å2, and Debye characteristic temperature (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 nc materials are determined by not only the grain size but also the microstructure of grain boundaries.