RESUMO
Glasses activated with europium show promising potential for use in applications relating to photonics, in particular solid-state laser generation. In the current work, Eu2O3 incorporated gemanium borate glasses were developed and explored their potentiality towards lasing active medium by probing physical, structural, optical and lasing properties in detail. The physical and structural features of each glass indicated the presence of non-bridging oxygens (NBOs) and an enhancement in network stability on account of the inclusion of europium ions into the GeO2 glass network. Optical energy band gaps, Ed, Eo, no, So, and λo values were obtained by absorption spectra and found to be increased with europium content. The sequence of Judd-Ofelt (JO) intensity parameters (Ω2, Ω4, and Ω6) exhibited the trend Ω2 > Ω4 > Ω6, and it confirmed the covalent nature of the as-developed glasses. 1 mol% Eu2O3 doped glasses exhibited the highest photoluminescence, quantum efficiency and fluorescence intensity ratio (R). The decay profiles showed single exponential nature for 5D0 state of Eu3+ ions and their lifetime values were calculated. The results amply demonstrated the viability of the manufactured glasses as a potential solid-state active laser medium, with the CIE diagram confirming the intense red color emission as seen from the PL spectra.
RESUMO
The present work reports the effect of particle size and shape of CoFe2O4 (CFO) nanoparticles on magnetic properties and their use in device applications as permanent magnets at room temperature. A set of CFO samples with different particle sizes and shapes were synthesized via the polymeric method by sintering at temperatures ranging from 300 °C to 1200 °C. These materials were characterized structurally by x-ray diffraction, morphologically by scanning electron microscopy, and microstructurally by transmission electron microscopy. The morphology of these CFO samples shows size-dependent shapes like spherical, pyramidal, lamellar, octahedral and truncated octahedral shapes for the particle sizes ranging from 7 to 780 nm with increasing sintering temperature. The emergence of magnetic properties was investigated as a function of particle size and shape with a special emphasis on permanent magnet applications at low and room temperatures. The values of saturation and remanent magnetization were found to increase monotonously with a particle size up to 40 nm and from thereafter they were found to remain almost constant. The other magnetic parameters such as coercivity, squareness ratio, anisotropy constant and maximum energy product ([Formula: see text]) were observed to increase up to 40 nm and then decreased thereafter as a function of particle size. The underlying mechanism responsible for the observed behavior of the magnetic parameters as a function of particle size was discussed in the light of coherent rotation, domain wall motion and shape induced demagnetization effects. The significant values of [Formula: see text] - the figure of merit of permanent magnets - observed for single domain particles (particularly, 14 nm and 21 nm) were found to have suitability in permanent magnetic technology.
