Vacuum-UV excitation and visible luminescence of nano-scale and micro-scale NaLnF4:Pr3+ (Ln = Y, Lu)

• Particle size of the NaLnF4-samples depending on the synthesis conditions.
• Pr3+ [Xe]4f2–[Xe]4f2 line emissions ranging from the UV to the NIR.
• Comparable spectra for the corresponding crystal structure types.
• Shift of the lowest crystal-field component of the [Xe]4f15d1 configuration.

The UV–Vis luminescence of NaLnF4:Pr3+ (Ln = Y, Lu) materials can be efficiently excited by vacuum UV radiation (VUV) such as the 172 nm emission of mercury-free Xe-discharge lamps. In this work, the optical properties of the cubic α-phase and the hexagonal β-phase of NaLnF4:Pr3+ (Ln = Y, Lu) powders are compared regarding particle sizes in the nano- and micrometer regime. Upon VUV excitation, the emission spectra of both crystal phases are found to be dominated by intraconfigurational [Xe]4f2–[Xe]4f2 transitions, which is explained by the chemical properties of the ternary fluorides. Furthermore it is observed that the emission and excitation spectra of nano- and micro-scale powders are very similar, but that the luminescence intensity is affected by the average particle size.