Ultrafast synthesis and luminescence properties of rare earth orthoniobates RENbO 4 (RE = La, Eu, Gd, Yb, Lu).

Rare earth orthoniobates (RENbO 4 ) are one kind of important functional materials due to its applications in solid-state phosphors, thermal barrier coatings, and microwave dielectric ceramics. The synthesis of rare earth niobates often needs high reaction temperatures (1300 °C-1700 °C) and long processing times (from hours to tens of hours) in solid-state reactions, which can increase the study time of the relationship between structure and properties. In this work, we used ultrafast high-temperature sintering method to synthesize RENbO 4 (RE = La, Eu, Gd, Yb, Lu), and found specific structure and properties in these materials obtained with specific synthetic techniques. Based on the electronegativity scale, the charge transfer energy of lanthanide ions in the YNbO 4 crystal was calculated. The rapid synthesis of RENbO 4 in a vacuum atmosphere generated more oxygen vacancies, and the structures of [REO 8 ] and [NbO 6 ] were distorted. The shortening of the fluorescence lifetime of LaNbO 4 and EuNbO 4 was related to the formation of self-trapped excitons facilitated by lattice distortion. The emission peak of LuNbO 4 at about 530 nm is attributed to the oxygen vacancy in the niobate group. The reported synthetic methods can provide a fast materials screening route for high melting point inorganic materials.