Intense narrow band blue emission in CuCrO2 delafossite by Ni2+-Mg2+ dual cation doping

For applications involving LED lighting and displays, phosphor materials with narrow emission bands are quite riveting. CuCrO2 is a well-known delafosste for optoelectronic device applications due to its wide bandgap, and high emission at short wavelengths. Here we tried emission band tuning of CuCrO2 by Ni2+ on 0.5 wt% Mg doped CuCrO2 crystallites. The photoluminescence spectra (PL) are observed when excited with 373 nm radiation, indicating that it had a strong blue emission peak at 423 nm with FWHM of 18.26 nm and good color purity of 91.32%. Rietveld refinement of XRD spectra and Raman investigation conveyed a considerable structural variation with Ni2+ doping and band gap decrement by UV-Vis analysis. In Raman studies, shifting of signature peaks and additional defect-induced peaks are observed, manifesting desired microstructural changes, and the UV-Vis absorption investigation revealed marginal decay of the optical band gap from 3.31 eV to 2.63 eV. Refractive index has also been determined from the UV-Vis analysis and their values substantiate the results.

Fermi level tuning in modified Bi2Te3 system for thermoelectric applications

The techniques of size reduction and defect engineering have attracted great interest as an effective strategy for developing new and modified thermoelectric materials with high performance. Here, we investigated the thermoelectric properties of the Bi₂Te₃ system modified by Fermi level tuning through the methods of nanostructuring and doping. Band structure modification and Fermi level shift contribute to the better thermoelectric performance of the material. A minimum thermal conductivity of 0.72 W K⁻¹ was obtained at 440 K with a reduction of 50% as compared to the pristine sample. The improved transport properties along with considerably reduced thermal conductivity result in a two-fold improved figure of merit of 0.295 at 420 K for the nanostructured sample Bi_0.4Sb_1.6Te₃ over pristine Bi₂Te₃.

The thermoelectric properties of Bi₂Te₃ system can be modified by Fermi level tuning using the methods of nanostructuring and doping. Fermi level shift contribute to better thermoelectric performance of the material, leading to two-fold improvement in figure of merit.

Bi-substitution-induced magnetic moment distribution in spinel Bi(x)Co(2-x)MnO(4) multiferroic

We report the near-edge x-ray absorption spectroscopy (NEXAFS) at the Co/Mn L(3,2) edge and oxygen K edge of the well-characterized Bi-substituted Co(2)MnO(4) multiferroic samples. The evolution of peak features in NEXAFS spectra of the Co/Mn L(3,2) edge and O K edge show the Bi-induced redistribution of magnetic cations (Co/Mn). The variation in valence states of Co and Mn in all the substituted compositions is consistent with the observed ferrimagnetic behaviour of the samples. Magnetization data show the decrease in molecular field complementing the ferrimagnetism. The role of Bi in the enhancement of magnetic interactions as well as the appearance of ferroelectricity in Bi(x)Co(2-x)MnO(4) (0≤x≤0.3) is discussed.