Photoluminescence, electro-optic response and piezoelectric properties in pressureless-sintered Er-doped KNN-based transparent ceramics

Er-doped (K0.5Na0.5)1−xLixNb1−xBixO3(0.05 ≤ x ≤ 0.08) ceramics have been prepared by pressureless sintering. Because of the cubic-like phase as well as the dense and fine-grained structure, the ceramics are optically clear, exhibiting high transmittances in the near-infrared and mid-infrared (MIR) regions (∼50% and ∼75%, respectively). They also possess strong electro-optic (EO) response, giving a large effective linear EO coefficient (128–184 pm/V). Owing to Er3+, the ceramics exhibit green and red up-conversion photoluminescence (PL) emissions, which are sensitive to the crystal symmetry of the ceramic host. The ceramics also exhibit a low absorption coefficient of OH−groups and then distinct and broadband MIR emissions. Together with the relatively large piezoelectric coefficient (70–90 pC/N), high dielectric constant (∼1400) and low dielectric loss (∼0.03), the ceramics open up potential applications in electrical/optical interdisciplinary field, such as visible displays, MIR solid lasers and optical attenuators.