Contact-separation-induced self-recoverable mechanoluminescence of CaF2:Tb3+/PDMS elastomer

Abstract Centrosymmetric-oxide/PDMS elastomers emit ultrastrong nonpreirradiation mechanoluminescence (ML) under stress and are considered one of the most ideal ML materials. However, previous centrosymmetric-oxide/PDMS elastomers show severe ML degradation under stretching, which limits their use in applications. This work presents an elastomer based on centrosymmetric fluoride CaF2:Tb3+ and PDMS, with ML that can self-recover after each stretching. Experimentation indicate that the self-recoverable ML of the CaF2:Tb3+/PDMS elastomer occurs essentially due to contact electrification arising from contact-separation interactions between the centrosymmetric phosphor and PDMS. Accordingly, a contact-separation cycle model of the phosphor-PDMS couple is established, and first-principles calculations are performed to model state energies in the contact-separation cycle. The results reveal that the fluoride-PDMS couple helps to induce contact electrification and maintain the contact-separation cycle at the interface, resulting in the self-recoverable ML of the CaF2:Tb3+/PDMS elastomer. Therefore, it would be a good strategy to develop self-recoverable ML elastomers based on centrosymmetric fluoride phosphors and PDMS.