The investigation on the relationship between the R/O ratio of Eu3+ in orthophosphates and the excitation wavelengths

• The R/O ratio of Eu3+ is different under the different wavelengths excitation.
• Under 393 nm excitation, the high R/O ratio of Eu3+ derives from the distorted EuOn polyhedron.
• Under 147 nm excitation, the high R/O ratio of Eu3+ mainly results from the shallow penetration depth.

Orthophosphates doped with Eu3+ were widely investigated for their excellent photoluminescence properties for lighting and displays applications. In this work, we successfully synthesized orthophosphates K3La1−x(PO4)2:xEu3+ (x = 0.03, 0.06, 0.09), K3Gd1−y(PO4)2:yEu3+ (y = 0.03, 0.06, 0.09), Gd1−mPO4:mEu3+ (m = 0.03, 0.06, 0.09) and studied their excitation and emission spectra. The obtained emission spectra of K3La1−x(PO4)2:xEu3+ (x = 0.03, 0.06, 0.09) showed that the integrated intensity ratios of 5D0 → 7F2/5D0 → 7F1 of Eu3+ were similar under 393 nm and 147 nm excitation, and higher than that under 254 nm excitation. The similar phenomena were observed in K3Gd1−y(PO4)2:yEu3+ (y = 0.03, 0.06, 0.09) and Gd1−mPO4:mEu3+ (m = 0.03, 0.06, 0.09). We interpreted this phenomenon based on the theory of energy transfer.

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