High-Pressure Behavior and Polymorphism of Titanium Oxynitride Phase Ti2.85O4N

Abstract

We report a crystallographic study of Ti2.85O4N, a new titanium oxynitride phase discovered using chemical vapor deposition and combinatorial chemistry techniques, under high-pressure conditions. Synchrotron X-ray diffraction was used to monitor structural changes in the material during compression up to 68 GPa. The data indicate that the orthorhombic (Cmcm) ambient-pressure phase (K0 = 154 ± 22 GPa with K0' = 5.2 ± 0.5) undergoes a first-order transition at 18 GPa to a new orthorhombic (Pmc21) structure. This new high-pressure polymorph remains stable up to 42 GPa, after which the emergence of a second high-pressure monoclinic (P21/c) phase is observed.