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In the current study, the structural and spectroscopic properties of phosphatic shale samples obtained from the Atomic Minerals Directorate for Exploration and Research were probed for potential use as a phosphor material. X‐ray diffraction and Raman and Fourier transform infrared spectroscopy revealed that the beneficiated phosphatic shale samples were primarily monophasic consisting of fluorapatite [Ca5(PO4)3F, (FAP)] with minor traces of haematite (α‐Fe2O3) and calcite (CaCO3). Energy dispersive X‐ray fluorescence revealed the presence of U, Eu, Dy and Tb in the FAP matrix substituted at Ca(I) and Ca(II) sites of FAP. A reduced optical direct band gap of 4.46 eV was calculated from the Tauc plot. Photoluminescence spectral studies revealed multicolour emissions (red, yellow, green and blue) on ultraviolet light excitation that were attributed to luminescence spectra from rare earth ions Eu3+, Tb3+, U4+ and U6+ in the FAP matrix. The overall emissions for the rare earth and actinide‐doped FAP were obtained in the cool white region and the corresponding Commission Internationale de l'Eclairage chromaticity coordinates were calculated to be (0.274, 0.317). The corresponding colour correlated temperature obtained was 9342 K. Furthermore, phosphatic shale had a high room temperature dielectric constant of 11 at a frequency of 1 kHz that demonstrated its suitability for use in biological sensors. The study showed that natural phosphatic shale could be a potential material for optical, biological and dielectric applications. [ABSTRACT FROM AUTHOR]

Erbium (Er) and lanthanum (La) substituted BiFeO (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi LaEr FeO ( x = 0·05, 0·07 and 0·1) (BLEFO) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFO. The Raman spectra of BLEFO samples showed the shift of Raman modes to higher wavenumbers and suppression of A modes indicating decrease in ferroelectricity. The Raman spectra also indicated the structural transformation due to Er and La substitution in BFO. On subsequent erbium doping, the intrinsic dielectric constant is found to decrease from 68 (for pure BFO) to 52 for BLEFO to 43 for BLEFO but increased to 89 for BLEFO when compared to pure BFO. The increase in Er content resulted in the increase in spontaneous magnetization (0·1178 emu/g at 8T for BLEFO) due to collapse of spin cycloid structure. Ferroelectric remnant polarization of BLEFO and BLEFO decreases when compared to pure BFO while small remnant polarization (close to paraelectric behaviour) is evident for BLEFO. [ABSTRACT FROM AUTHOR]