Effect of Pr doping on structure and luminescence properties of ZrO2 nanoparticles

Pr3+ impurity transitions in monoclinic and cubic phases of ZrO2 have been investigated by photoluminescence and thermoluminescence (TL). Zr(1-x)Pr (x) O-2 (0 & LE; x & LE; 0.015) samples were prepared by the combustion method. Rietveld refined x-ray diffraction results confirm that undoped ZrO2 has a monoclinic structure, whereas Pr doped ZrO2 samples are in mixed phase consisting of monoclinic and cubic structures. ZrO2 shows a broad defect-related emission peak centered at 500 nm under an excitation wavelength of 300 nm. A series of Pr3+-related emissions are observed at 512, 584, 612-640 nm due to P-3(0) & RARR; H-3(4), P-3(1) + I-1(6) & RARR; H-3(5), D-1(2) & RARR; H-3(4) transitions and between 719 and 740 nm due to D-1(2) & RARR; H-3(5) transitions when excited with 454 nm. The PL decay lifetime of Zr0.996Pr0.004O2 is 1.55 & mu;s for fixed & lambda; (ex) = 300 nm and & lambda; (em) = 612 nm. The TL glow curve of Zr0.99Pr0.01O2 shows a prominent peak at 695 K and secondary peaks at 508 K and 570 K, which are not observed in undoped ZrO2. The TL emission measured at 695 K confirms that Pr3+ replaces Zr4+ in cubic lattice sites of ZrO2. This work shows the relationship between the luminescence properties and different structures of ZrO2 and that supports the design of new materials for possible applications.