Materials Research Express (Jan 2020)
Down and upconversion photoluminescence of ZrO2:Er3+ phosphor irradiated with 120 MeV gold ions
Abstract
Down conversion and upconversion photoluminescence of pristine and gold ion irradiated ZrO _2 :Er ^3+ phosphor synthesized by solution combustion are reported. The crystallinity of the sample as analysed by x-ray diffraction shows a monoclinic phase having a crystallite size of about 57 nm calculated using Williamson—Hall formula. Field emission scanning electron microscopy shows that the shape and size of phosphor grains are non uniform. The down conversion photoluminescence of ZrO _2 :Er ^3+ has sharp emission bands in the red, green and blue regions of the spectrum. These emissions are corresponding to f–f transitions of Er ^3+ ions under excitation of 379 nm. In particular, the emission has maxima at 467, 492, 526, 548 and 660 nm correspond to ^4 F _3/2 → ^4 I _15/2 , ^4 F _7/2 → ^4 I _15/2 , ^2 H _11/2 → ^4 I _15/2 , ^4 S _3/2 → ^4 I _15/2 and ^4 F _9/2 → ^4 I _15/2 transitions respectively. Interestingly, the PL emission intensity (excitation at 379 nm) is enhanced 1.6 times higher than pristine sample after 120 MeV Au ion irradiation for a fluence of 1 × 10 ^10 ions cm ^−2 . The blue to green emission ratio increases with the increase in ion fluence. Therefore, emission of the color shift towards bluish-white color with ion fluence. The lifetime of ^4 S _3/2 level is found to be 16.9 and 71.5 μ s for pristine and Au ion irradiated (1 × 10 ^12 ions cm ^−2 ) ZrO _2 :Er ^3+ respectively. In near infrared (NIR) region, the PL emission band is observed at 1531 nm corresponding to ^4 I _13/2 → ^4 I _15/2 transition of Er ^3+ under excitation of 980 nm. The sample emits intense green emission and relatively weak red emission in up conversion PL under excitation of 980 nm. The ratio of intensities of red and green emission changes after Au ion irradiation is attributed to the corresponding change in the lattice symmetry in the host. Resulting in strong up conversion emission from two photon absorption process.
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