RESUMEN
The tuning of second (SHG) and third (THG) harmonic emission is studied in the model system LiNb 1-xTa xO 3 (0≤x≤1, LNT) between the established edge compositions lithium niobate (LiNbO 3, x=0, LN) and lithium tantalate (LiTaO 3, x=1, LT). Thus, the existence of optical nonlinearities of the second and third order is demonstrated in the ferroelectric solid solution system, and the question about the suitability of LNT in the field of nonlinear and quantum optics, in particular as a promising nonlinear optical material for frequency conversion with tunable composition, is addressed. For this purpose, harmonic generation is studied in nanosized crystallites of mechanochemically synthesized LNT using nonlinear diffuse reflectometry with wavelength-tunable fundamental femtosecond laser pulses from 1200 nm to 2000 nm. As a result, a gap-free harmonic emission is validated that accords with the theoretically expected energy relations, dependencies on intensity and wavelength, as well as spectral bandwidths for harmonic generation. The SHG/THG harmonic ratio â«1 is characteristic of the ferroelectric bulk nature of the LNT nanocrystallites. We can conclude that LNT is particularly attractive for applications in nonlinear optics that benefit from the possibility of the composition-dependent control of mechanical, electrical, and/or optical properties.
RESUMEN
The samples of precipitated tin (IV) phosphate, modified using hydrothermal, microwave, and mechanochemical procedures, were studied in the process of Cs(I), Sr(II), and U(VI) ion sorption. The initial and modified samples were investigated before and after sorption using XRD, XRF, FTIR, and nitrogen adsorption-desorption. It was found that the modification procedures transformed the micro-mesoporous structure of the initial sample into a meso-macroporous structure. As a result, the sorption capacity in relation to all ions increases several times. This indicates the determining role of the porous structure, primary content, and mesopore size on the sorption activity of tin phosphate. The samples, treated in the form of a wet gel, which is a novel procedure, showed the maximum sorption indicators. The sorption of all the tested ions is described by the Langmuir isotherm.
RESUMEN
The paper presented the mechanical (MChT), microwave (MWT), and hydrothermal (HTT) methods of zirconium phosphate samples modification in order to improve its adsorption affinity for the Ag (I) ions. The FTIR studies proved that the modification of both gel and xerogel samples with the ultrasonic microwaves causes an increase in the concentration of phosphate groups on the surface of MWT-modified zirconium phosphate: the isoelectric point pHiep = 2.2-2.9 for these samples against 3.9 for the initial sample and pKa2 values were 4.7-5.6 and 6.3, respectively. As resulting from the Ag+ ion adsorption studies, the MWT treatment of zirconium phosphate samples caused the greatest affinity of Ag+ ions for the surface of MWT zirconium phosphate. Compared with the initial ZrP sample, the shift of the Ag (I) ion adsorption edge towards lower pH values was observed, e.g., with adsorption of Ag (I) ions from the solution with the initial concentration of 1 µmol/dm3 for the initial ZrP sample pH50% = 3.2, while for the sample MWT ZrPxero pH50% = 2.6.
