ABSTRACT
The Ba0.97Nd0.0267Ti(1-x)W x O3 (BNT x ) pervoskite with a single phase tetragonal structure was prepared at 900 °C using the Molten salt method. Raman spectra, Fourier transform infrared spectra (FT-IR), absorption spectra (Vis-NIR) and photoluminescence spectra (PL) in the temperature range from 10-300 K were used to investigate the correlations between the crystal structure and the optical properties of BNT x ceramics. Raman analyses and FT-IR indicated that the W6+ ions are incorporated sufficiently into into the BNT x lattice. The optical absorption spectra were recorded in the wavelength range of 400-1000 nm. The optical band gap (E g) and Urbach energy (E u) values were calculated from the absorption spectra. The emission spectra exhibited three prominent peaks located at 880, 1058 and 1340 nm corresponding to the 4F3/2 â 4I9/2,11/2,13/2 transition levels, respectively. They also showed a decrease in the intensity of emission spectra following the addition of W6+ ions. This decrease is due to the slight changes in the crystal environment around Nd3+ and the non-radiative energy transfer. According to the PL measurements, the study of power-excitation density confirmed that two photons at low energy are required to create the down-conversion (DC) emissions, implying that they may also have important applications as DC materials.
ABSTRACT
Oxidised porous silicon samples prepared from highly and weakly doped p-type silicon substrates, have been functionalised with calix[4]arene (CA) molecules. They have been used for sodium detection as electrolyte/insulator/silicon (EIS) structures. An over Nernstian behaviour was observed and correlated with physical parameters of porous silicon samples (porosity, resistivity). A generalised Nernstian equation was proposed in order to describe this property. CA functionalised EIS structures based on porous silicon present higher lifetime compared to flat structures.
