Tunable transmission light in nanocrystalline La1−xEuxB6

• Single-phased ternary La1−xEuxB6 nanopowders are prepared by a solid-state reaction for the first time.
• The transmission light wavelength of LaB6 increase from 590 nm to 1070 nm with increasing Eu doping content.
• Decreasing number of conduction electrons leads to tunable characteristic of transmission light.

Cubic-shaped ternary La1−xEuxB6 nanopowders have been synthesized via a solid-state reaction and their optical properties are investigated for the first time. La1−xEuxB6 nanopowders have a high crystallinity with a grain size of 40 nm and HAADF–STEM images fully confirm that the Eu element has been successfully doped into the lattice of LaB6. The optical absorption results indicate that the transmission light wavelength of LaB6 shifts from 590 nm to 1070 nm with increasing Eu doping content, indicating a “redshift” phenomenon of transmission light. Thus, this novel tunable characteristic of La1−xEuxB6 transmission light will open a new way to extend the optical applications of LaB6 nanopowder.