Highly oriented pyrolytic graphite (
HOPG) is a pyrolytic graphite with an angular spread of the
c-axes of the crystallites of less than 1 degree.
Note:
Commercial HOPG is usually produced by stress annealing at approximately 3300 K.
Source:
PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 495 (https://doi.org/10.1351/pac199567030473)