RESUMEN
Sorption-luminescent method for terbium determination based on natural Transcarpathian clinoptilolite without using of complex synthetic organic compounds and toxic solvents was proposed. Optimal luminophore preparation conditions are sorption of Tb(III) on zeolite in the borate buffer solution with pH 8.25 and further calcination of clinoptilolite-Tb(III) samples at 500°C. For luminescence excitation the rays with wavelength of λ = 220nm of were used. Luminescence intensity at λ = 545nm was selected as analytical parameter for a quantitative terbium determination. Definable range of Tb(III) concentration with the detection limit of 1ngmL-1 is within of 3-1140ngmL-1. The proposed method can be used for the terbium determination in the presence of many rare earths. Sorption-luminescent method can be applied for determination of trace terbium ions in synthetic water solutions and in intermetallics. The proposed analytical method gave recoveries from 90% to 108% and R.S.D. from 0.78% to 6.2% determination of terbium.
RESUMEN
Micro- and nanocrystalline lanthanum-samarium ferrites La1-x Sm x FeO3 with orthorhombic perovskite structure were obtained by using both solid state reactions (x = 0.2, 0.4, 0.6 and 0.8) and sol-gel synthesis (x = 0.5) techniques. Obtained structural parameters of both series of La1-x Sm x FeO3 are in excellent agreement with the "pure" LaFeO3 and SmFeO3 compounds, thus proving formation of continuous solid solution in the LaFeO3-SmFeO3 system. Peculiarity of La1-x Sm x FeO3 solid solution is divergence behaviour of unit cell dimensions with increasing x: systematic decrease of the a and c lattice parameters is accompanied with increasing b parameter. Such behaviour of the unit cell dimensions in La1-x Sm x FeO3 series led to crossover of the a and c perovskite lattice parameters and formation of dimensionally tetragonal structure near x = 0.04. Linear decrease of the unit cell volume of La1-x Sm x FeO3 with decreasing x according with the Vegard's rule indicate absence of short-range ordering of R-cations in the LaFeO3-SmFeO3 system.