Influencing the Solid-Solid Phase Transition in Phenanthrene by Suitable Doping

Abstract

The order-disorder phase transition in solid phenanthrene was studied with differential scanning calorimetry and X-ray powder diffraction. This fully reversible transformation can be influenced by doping phenanthrene with structurally similar polycyclic aromatic hydrocarbons or heterocyclic aromatics. So far, four dopants have been used: benzo[c]cinnoline, phenanthridine, anthracene and carbazole. It was found that the transformation is not influenced by dopants that form eutectic phase diagrams with phenanthrene (benzo[c]cinnoline, phenanthridine). However, if the dopant is incorporated into the phenanthrene lattice to form a mixed crystal, the transition is inhibited above 3.7 mol% anthracene and 6.1 mol% carbazole, respectively. By X-ray diffraction, it is shown that these dopants induce the formation of the high-temperature phase already at room temperature.