Intervalence charge transfer state interfered Pr3+ luminescence: A novel strategy for high sensitive optical thermometry

In this study, the Ruddlesden-Popper type perovskite Na2La1.96Pr0.04Ti3O10 micro-crystals are synthesized and demonstrated to be one of the most promising optical temperature sensing materials. The measured maximal absolute temperature sensitivity of this phosphor reaches as high as 0.40 K-1, remarkably superior to those of the inorganic optical thermometric materials reported previously; while the relative sensitivity is 1.96% K-1, ranking among the highest ones for the inorganic optical thermometric materials. Analysis of the configurational coordinate diagram indicates that thermo-induced relaxation between the Pr(3+3)Px and D-1(2) levels through Pr3+-Ti4+ intervalence charge transfer state is the primary cause for the temperature sensing characteristics. Based on these results, a novel temperature sensing strategy utilizing the intervalence charge transfer state interfered Pr3+ luminescence to perform optical thermometry is proposed, which is further demonstrated to be universally valid for the Pr3+ doped oxides containing d(0) configured transition metal ions, as long as energy of the intervalence charge transfer state is moderate. This work may provide useful inspiration for developing high sensitive optical thermometric materials. (C) 2016 Elsevier B.V. All rights reserved.