Upconversion of transparent glass ceramics containing β-NaYF:Yb, Er nanocrystals for optical thermometry.

β-NaYF nanocrystal embedded glass ceramics were fabricated by a melt-quenching method with subsequent heat-treatment. Structural characterizations and spectrographic techniques were performed to verify the successful precipitation of β-NaYF nanocrystals and partition of dopants. Upon excitation of 980 nm, bright green upconversion emission could be achieved in Yb, Er codoped β-NaYF nanocrystal embedded glass ceramics. Furthermore, the temperature-dependent upconversion behaviour based on thermally coupled energy levels was also examined in the range of 300-773 K with the maximum relative sensitivity of 1.24% K at 300 K. Accordingly, it has been proved to be a promising candidate for application in optical thermometry.