Effect of Ti Substitution on V-V Dimerization in Ilmenite-Type MgVO₃

The origin of V-V dimerization, a characteristic phenomenon observed in ilmenite-type vanadium oxides, remains unclear. To elucidate this origin, we must first clarify the conditions under which such dimers can form. Here, we investigate the effect of Ti⁴⁺ substitution at the V⁴⁺ sites in MgVO₃, a representative ilmenite-type vanadium oxide. Synchrotron X-ray diffraction measurements revealed that increasing the Ti content lowers the structural phase transition temperature associated with V-V dimerization. Furthermore, magnetic susceptibility measurements indicated that Ti substitution suppresses the formation of V-V bonds, which are disrupted concomitantly with the structural phase transition. MgV_0.70Ti_0.30O₃ adopts a rhombohedral ilmenite-type structure without long-range V-V dimer ordering even at low temperatures. This study provides experimental insights into the stability and collapse of V-V dimers.