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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.

Photoluminescence of compounds that contain stoichiometric zirconium has been studied under vacuum ultraviolet excitation. The compounds show emission peaking at 280–320 nm while the excitation spectra show some bands in 130–190 nm region. The ultraviolet emission is explained as Zr to O charge transfer transition. The luminescence result and structural information classify the studied compounds into two groups. The former group involves ZrP 2 O 7 , CaZr(PO 4 ) 2 , NaZr 2 (PO 4 ) 3 , Ca 2 ZrSi 4 O 12 , Ca 3 ZrSi 2 O 9 and SrZrSi 2 O 7 , which show rather intense luminescence and do not have any infinite Zr–O–Zr–O–3D chain or link in their structure. The latter group is CaZrO 3 and ZrSiO 4 , which do contain infinite Zr–O–Zr–O–3D chain and show quite weak luminescence. Luminescence of Ca 1− x Mn x Zr(PO 4 ) 2 has also been studied. By replacing a part of Ca with Mn, ultraviolet emission of the host weakens and visible emission peaking at 540 nm appears. It is claimed that transfer of absorbed energy from Zr to Mn occurs.

The temperature dependence of the time-integrated intensity of afterglow in SrAl 2 O 4 :Eu,Dy and SrAl 2 O 4 :Eu phosphors has been investigated by using UV light from a deuterium lamp. The time-integrated intensity of afterglow in SrAl 2 O 4 :Eu,Dy increases at around 150 K with temperature, and reaches the maximum at around 270 K. These results are compared with those for SrAl 2 O 4 :Eu, and the function of Dy 3+ ions is discussed in connection with the creation of hole traps.