Effect of Zr⁴⁺ Addition on Photoluminescence Properties of YPO₄:Mn²⁺

Photoluminescence (PL) properties of YPO₄:Mn²⁺ and Zr⁴⁺-doped YPO₄:Mn²⁺ have been investigated by measuring PL and PL excitation (PLE) spectra and electron spin resonance (ESR) spectra. The PL spectrum at 9 K is dominated by a red (R) emission band at 1.91 eV for YPO₄:Mn²⁺ and a blue-green (BG) emission band at 2.52 eV for YPO₄:Zr⁴⁺,Mn²⁺. The R and BG bands are caused by the d–d transition in Mn²⁺ ions, in analogy with PL spectra of Mn²⁺-doped inorganic compounds. The PLE spectra for the R and BG bands are different from each other, suggesting that the Zr⁴⁺ addition changes the environment of Mn²⁺ ions. The ESR spectra revealed that Mn²⁺ ions can occupy interstitial sites without Zr⁴⁺ addition and Y³⁺ lattice sites with Zr⁴⁺ addition. It is thus supposed that the R and BG bands originate in an interstitial Mn²⁺ ion and a Y³⁺-substituted Mn²⁺ ion, respectively. The increase in the BG emission intensity caused by Zr⁴⁺ addition can be explained as an increase in the number of Mn²⁺ ions at Y³⁺ sites.