Valence instability and photochemical reaction at surface of strongly correlated MgTi2O4

Abstract

We have studied surface electronic structure and light illumination effect of spinel-type MgTi2O4 with Ti3+(d1) electronic configuration. Ti4+ species are found at surfaces of MgTi2O4, which show photo-induced effect similar to the Ti4+-oxide semiconductors with surface depletion layer. MgTi2O4 with the surface Ti4+ states reacts with water for H2 emission, which is largely enhanced by light illumination.

Melting of Pb Charge Glass and Simultaneous Pb–Cr Charge Transfer in PbCrO3 as the Origin of Volume Collapse

“…These values are consistent with one another and agree with that observed by HRTEM. It should be noted that formation of a surface layer with a d 0 ion was found for MgTi 2 O 4 as well, and that a Cr 6+ contribution is present even in our XPS specra for SrCrO 3 measured as a reference. Here, one can safely conclude that the Cr 6+ is derived from the surface amorphous PbCr 6+ O 4 layer observed by our HRTEM study.…”