Up-conversion luminescence and temperature sensing properties in Er-doped ferroelectric Sr2Bi4Ti5O18

Er-doped Sr 2 Bi 4 Ti 5 O 18 (SBT- x ) ceramics were synthesized via a solid-state reaction method, and their structure, up-conversion luminescence (UCL), temperature sensing performance and ferroelectric behaviors were investigated. The obtained SBT- x samples crystallize in the polar orthorhombic phase, with space group B2cb. Under 980   nm excitation, bright green and weak red emissions are observed which correspond to the transitions from 2 H 11/2 / 4 S 3/2 and 4 F 9/2 to 4 I 15/2 level, respectively. The optimal doping concentration of Er 3+ in SBT host is determined as 0.08. The critical energy transfer distance ( R c ) is about 20.57   Å and the major interaction mechanism among Er 3+ ions is determined as the d–d interaction. A possible UCL mechanism is proposed in light of the dependence of emission intensities on pumping power. Furthermore, optical temperature sensing properties are also investigated according to the fluorescence intensity ratio (FIR) of green emissions at 527 and 550   nm in the temperature range from 303   K to 573   K. The maximum sensing sensitivity is found to be 0.0042   K −1 . Additionally, the response of SBT- x to external electric field stimuli is also confirmed. It is believed that SBT- x has potential application as optical temperature sensing materials.