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Nanocrystalline ZnO:Mn (0.1 mol%) phosphors have been successfully prepared by self propagating, gas producing solution combustion method. The powder X-ray diffraction of as-formed ZnO:Mn sample shows, hexagonal wurtzite phase with particle size of ∼40 nm. For Mn doped ZnO, the lattice parameters and volume of unit cell (a=3.23065 Å, c=5.27563 Å and V=47.684 (Å)(3)) are found to be greater than that of undoped ZnO (a=3.19993 Å, c=5.22546 Å and V=46.336 (Å)(3)). The SEM micrographs reveal that besides the spherical crystals, the powders also contained several voids and pores. The TEM photograph also shows the particles are approximately spherical in nature. The FTIR spectrum shows two peaks at ∼3428 and 1598 cm(-1) which are attributed to O-H stretching and H-O-H bending vibration. The PL spectra of ZnO:Mn indicate a strong green emission peak at 526 nm and a weak red emission at 636 nm corresponding to (4)T(1)→(6)A(1) transition of Mn(2+) ions. The EPR spectrum exhibits fine structure transition which will be split into six hyperfine components due to (55)Mn hyperfine coupling giving rise to all 30 allowed transitions. From EPR spectra the spin-Hamiltonian parameters have been evaluated and discussed. The magnitude of the hyperfine splitting (A) constant indicates that there exists a moderately covalent bonding between the Mn(2+) ions and the surrounding ligands. The number of spins participating in resonance (N), its paramagnetic susceptibility (χ) have been evaluated.

a b s t r a c tZn (1−x) Fe (x) O (1+0.5x) (x = 0.5-5 mol%) nanoparticles were synthesized by a low temperature solution combustion route. The structural characterization of these nanoparticles by PXRD, SEM and TEM confirmed the phase purity of the samples and indicated a reduction in the particle size with increase in Fe content. A small increase in micro strain in the Fe doped nanocrystals is observed from W-H plots. EPR spectrum exhibits an intense resonance signal with effective g values at g ≈ 2.0 with a sextet hyperfine structure (hfs) besides a weak signal at g ≈ 4.13. The signal at g ≈ 2.0 with a sextet hyperfine structure might be due to manganese impurity where as the resonance signal at g ≈ 4.13 is due to iron. The optical band gap E g was found to decrease with increase of Fe content. Raman spectra exhibit two non-polar optical phonon (E 2 ) modes at low and high frequencies at 100 and 435 cm −1 in Fe doped samples. These modes broaden and disappear with increase of Fe dopant concentration. TL measurements of ␥-irradiated (1-5 kGy) samples show a main glow peak at 368• C at a warming rate of 6.7• Cs −1 . The thermal activation parameters were estimated from Glow peak shape method. The average activation energy was found to be in the range 0.34-2.81 eV.

The present paper describes the synthesis of 0.1 mol% Gadolinium (Gd) doped Zinc oxide (ZnO) nanophosphor by solution combustion method using Oxalyl dihydrazide (ODH) fuel. Powder X-ray diffraction (PXRD) peaks are well matched with the standard hexagonal wurtzite structure of ZnO (JCPDS card no. 36-1451). SEM and TEM analysis reveals porous morphology of as-formed sample with particles having narrow size distribution in the range ∼60-70 nm, in good agreement with XRD data. The PL spectrum of Gd doped ZnO sample exhibits an extra blue emission at 441 nm (∼2.81 eV) in addition to the emission bands from undoped ZnO. From the TL data of ZnO:Gd nanophosphor with UV irradiation, it is observed that considerable amount of re-trapping is taking place in all the TL second order peaks. The EPR spectrum exhibits a number of resonance signals suggesting that Gd 3+ ions are experiencing different crystal field strength and Zeeman interactions.