Fabrication of the best conductor from single-crystal copper and the contribution of grain boundaries to the Debye temperature

The scientific community has attempted to fabricate superconductors that work at room temperature; however, this goal has not yet been achieved. Considering miniaturization of devices and the requirement of low-power consumption in electronics, it is important to enhance room-temperature conductivity. We prepared the best conductor using crystallization and enhanced its conduction using high-pressure annealing. Single-crystal copper showed a conductivity enhancement of 12–14% after treatment under high pressure and temperature compared with that of oxygen-free copper, which has the highest conductivity for a metal. The contribution of grain boundaries to the Debye temperature was calculated and the phonon excitation was maximized at a lower temperature in grain-free copper. This study aimed to develop a new conductor, in which phonon–electron scattering is reduced at high temperatures. Single-crystal copper could be used for large-scale production of Bitter magnets to generate a high magnetic field and for applications of crystal engineering.