Luminescence properties of Ce-doped ZrO2 phosphors synthesized by combustion method.

Zr1-x Cex O2 with x = 0.005, 0.01, 0.02, and 0.03 samples were synthesized using a combustion technique. The X-ray diffraction results revealed that Ce-doped ZrO2 nanoparticles were in a monoclinic structure up to 1 mol% Ce concentration. The increase in the Ce concentration caused more distortion in the monoclinic structure of zirconia. The samples showed a mixed phase (monoclinic + tetragonal) beyond 1 mol% Ce content. The crystallite size (D) and strain (ε) were calculated from the Williamson-Hall equation. The D decreased from 25 ± 1 to 20 ± 1 nm and ε increased from 0.03 to 0.28% with an increase in Ce concentration. Photoluminescence (PL) spectra of Zr1-x Cex O2 showed emission in the blue region under an excitation wavelength of 290 nm. Zr0.995 Ce0.005 O2 showed the highest PL intensity with an average lifetime of 0.93 µs, and the PL intensity decreased with the increase in the Ce concentration. Thermoluminescence (TL) glow curves of Zr1-x Cex O2 were measured after gamma irradiation (500 Gy) with a heating rate of 5 K s-1 . The TL curve of Zr0.995 Ce0.005 O2 showed two prominent peaks at 412 K (peak 1) and 600 K (peak 2). The first TL glow peak was shifted towards a higher temperature at 440 K above 1 mol% Ce concentration. Repetitive TL measurements on the same aliquot exhibited excellent repeatability. Kinetic parameters associated with the TL peaks were calculated using the curve fitting method. Peak 1 followed non-first-order kinetics. The value of the activation energy of the 440 K peak was found to be 0.95 ± 0.01 eV for Zr0.99 Ce0.01 O2 . These findings showed that Zr1-x Cex O2 might be used in lighting and radiation dosimeter applications.

Study of paramagnetic and luminescence centers of microcline feldspar.

Microcline feldspar crystal has been analyzed in order to determine the centers suitable for use in ESR and luminescence dating. ESR measurements at RT showed the Fe3+ line, and at 77K the Si-O(-) ..X signal with g=2.0052, 2.0098 and 2.0128. TL glow peak at 157 and 300 degrees C in UV interval were observed and in the VIS range we noted peaks at 150, 280 and 340 degrees C. TL growth curve of the 340 degrees C peak could be fitted by a saturating exponential equation and can be used in TL dating. Emission curves showed band widths 1.95+/-0.09, 2.73+/-0.08 and 4.94+/-0.50 eV. Transitions from 4T1-->6A1)of Fe3+ can be associated with the 1.95 eV band and the transition from 4A1 4E(G)-->6A1(S) with 2.73 eV band.