Предложена простая в исполнении методика получения легированных GeO2-аэрогелей. На начальном этапе получали гель состава (NH4)3H(Ge7O16)(H2O)x путем растворения диоксида германия в водном растворе аммиака с рН 8,2. Введение ионов допанта осуществляли пропиткой гидрогелей раствором нитрата празеодима в диметилсульфоксиде (ДМСО). Были определены оптимальные условия синтеза, позволяющие достичь равномерного распределение иона-допанта в матрице. Соотношение Pr/Ge в полученных аэрогелях составляло 0,1. Образцы аэрогелей были подробно охарактеризованы методами ИК, ИСП-АЭС, низкотемпературной адсорбции азота и др. Установлено влияние празеодима на люминесцентные характеристики GeO2-аэрогелей при возбуждении излучением с длиной волны 240, 255 и 390 нм. An easy-to-implement technique for obtaining REE-doped GeO2 aerogels is proposed. Optimal synthesis conditions have been determined to achieve a uniform distribution of the ion-dopant in the matrix. The effect of praseodymium on the luminescent characteristics of GeO2 aerogels when excited by radiation with wavelengths of 240, 255 and 390 nm has been established.

Anhydrous basic bismuth nitrate Bi 6 (NO 3 ) 2 O 7 (OH) 2 was shown to be produced by reacting bismuth nitrate with aqueous ammonia under microwave-assisted hydrothermal treatment as a result of hydrolysis. The composition of the basic nitrate was verified by titration, CHNS analyses, DTG, and IR spectroscopy. Photocatalytic tests showed that Bi 6 (NO 3 ) 2 O 7 (OH) 2 has a photocatalytic activity, but its properties are interior to those of α-Bi 2 O 3 .

Abstract—We have synthesized needle- and platelike α-Bi2O3 and Bi2O2CO3 nanoparticles. The bulk density of the α-Bi2O3 and Bi2O2CO3 powders is 8.5 and 6.9 g/cm3. The dielectric permittivity of α-Bi2O3 and Bi2O2CO3 has been calculated using dielectric permittivity and dielectric loss tangent dispersion measurements in the frequency range from 2.5 × 101 to 1 × 106 Hz for 40% suspensions (0.05 and 0.08 volume fractions of α-Bi2O3 and Bi2O2CO3, respectively) in PMS-300 polydimethylsiloxane. The value of ε∞ has been found to be 5.4 for α-Bi2O3 and 4.9 for Bi2O2CO3. Dielectric spectra of the suspensions have been shown to exhibit no relaxation behavior in the frequency range studied. We have compared the effects of the shape and dielectric permittivity of the particles on the magnitude of the electrorheological effect in them. Using a simple polarization model, we have analyzed the effect of the dielectric characteristics of the filler material on the yield stress τ0 of the suspensions in electric fields from 0 to 4 kV/mm. Using a combination of rheometric and direct microscopic observations, we have explained the effect of the type of filler on the electrorheological effect: the Bi2O2CO3-based ERFs have higher shear and compressive yield stresses, whereas the α-Bi2O3-based ERFs have a higher tensile yield stress.

We have developed a process for the synthesis of fine bismuth orthogermanate, Bi4Ge3O12 (BGO), powders in a NaCl/KCl melt and examined the effect of synthesis conditions on the phase composition and morphology of the powders. Our results demonstrate that the synthesized materials compare well in scintillation performance with single-crystal BGO: their scintillation efficiency is 90% relative to single-crystal BGO, with a decay time of 300 ns.

Reactions of nitric acid solutions of bismuth with alkalis have been studied. The effect caused by coprecipitation conditions in the presence of additional agents (EG, PEG 400, or PEG 8000) and without on the phase composition and morphology of α- and γ-Bi 2 O 3 has been determined.

Optical and vibrational spectra of Bi 1.8 Fe 1.2(1 – x ) Ga 1.2 x SbO 7 solid solutions with pyrochlore structure have been studied. It has been shown that the compounds have strongly disordered structure. It has been established that a decrease in iron content causes a marked shift of Bi 1.8 Fe 1.2(1 – x ) Ga 1.2 x SbO 7 absorption edge. According to assessment of band gap width, Bi 1.8 Ga 1.2 SbO 7 is the most wide-band compound (2.90 eV), while Bi 1.8 Fe 1.2 SbO 7 is the most narrow-band compound (1.88 eV).

Reaction of hydrochloric acid solutions of bismuth and antimony with ammonia has been studied and effect of coprecipitation conditions of resultant hydroxides on their reactivity has been determined. Annealing conditions for coprecipitation products have been optimized. Effect of surfactants of different nature and concentration on the phase composition, size, and shape of resulting particles have been examined. Nanocrystalline samples of BiSbO4 have been synthesized.

A technique has been developed for fluorinating the pyrochlore oxide Bi1.8Fe0.2FeSbO7, and a compound with the composition Bi1.8Fe1.2SbO7–x/2Fx has been obtained. The synthesized oxyfluoride also has the pyrochlore structure (sp. gr. Fd3m), with a lattice parameter a = 10.4443(1) Å (R wp = 5.2). It has been shown that the charge balance upon fluorine substitution for oxygen is maintained not through partial reduction of Fe3+ to Fe2+ but through the incorporation of fluorine into oxygen vacancies. The magnetic behavior of the fluorinated pyrochlore phase is determined by the persisting frustration of the octahedral sublattice, which is responsible for the development of a spin glass state below T f = 12 K. The fluorination-induced changes in the anion sublattice led to an increase in the antiferromagnetic exchange interaction between neighboring Fe3+ ions and changes in the dynamic properties of the spin glass phase.

Experimental data have been presented to confirm the thermal nature of broadband visible radiation emitted from Yb 3+ - and Er 3+ -doped nanocrystalline particles of orthophosphates and orthophosphate hydrates irradiated by 972-nm near-infrared laser radiation. The mechanism of appearance of this radiation has been discussed.

The Bi–La–Fe–Sb–O, Pr–Fe–Sb–O, and Bi–Pr–Fe–Sb–O systems have been shown to contain pyrochlore solid solutions. We have determined the limits of the Pr 2– x Fe 1 + x SbO 7 and Bi 2– x Ln x FeSbO 7 (Ln = La, Pr) solid solutions and shown that there is no compound corresponding to the “ideal” composition Pr 2 FeSbO 7 . Analysis of the magnetic properties of the synthesized compounds indicates that rare earth substitution for bismuth ions has no effect on the spin glass transition and that the spin glass state is only determined by the interaction between the Fe 3+ spins on the octahedral site. The Pr 3+ paramagnetic ion in Pr 2– x Fe 1 + x SbO 7 does not participate in the formation of the spin glass state but makes a paramagnetic contribution to the total magnetic susceptibility, which is especially significant at low temperatures.

The up-conversion luminescence of Er 3+ from the 2 H 11/2 , 4 S 3/2 , and 4 F 9/2 levels in nanocrystals of Y 0.95(1‒ x ) Yb 0.95 x Er 0.05 PO 4 ( x = 0, 0.3, 0.5, 0.7, 1) orthophosphates activated with Er 3+ ions has been studied under the excitation of Yb 3+ ions to the 2 F 5/2 level by 972-nm cw laser radiation. Broadband radiation in the wavelength range of 370–900 nm has been observed at certain power densities of exciting laser radiation; this broadband radiation is absent in the case of excitation of the powders under study by pulsed laser radiation with a wavelength of 972 nm at a pulse repetition frequency of 10 Hz and a duration of a pulse of 15 ns. Experimental data indicating that this radiation is thermal in nature have been presented.