Down and upconversion photoluminescence of ZrO2:Er3+ phosphor irradiated with 120 MeV gold ions

Abstract

Abstract Down conversion and upconversion photoluminescence of pristine and gold ion irradiated ZrO2:Er3+ 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 ZrO2:Er3+ has sharp emission bands in the red, green and blue regions of the spectrum. These emissions are corresponding to f–f transitions of Er3+ ions under excitation of 379 nm. In particular, the emission has maxima at 467, 492, 526, 548 and 660 nm correspond to 4F3/2 → 4I15/2, 4F7/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 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 × 1010 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 4S3/2 level is found to be 16.9 and 71.5 μs for pristine and Au ion irradiated (1 × 1012 ions cm−2) ZrO2:Er3+ respectively. In near infrared (NIR) region, the PL emission band is observed at 1531 nm corresponding to 4I13/2 → 4I15/2 transition of Er3+ 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.