G. I. Kadyrova

Synthesis and properties of homogeneously doped Nb2O5〈Dy〉 and a LiNbO3〈Dy〉growth charge

We have studied conditions for the synthesis of niobium pentoxide and a lithium niobate growth charge doped with dysprosium, which was added to niobium hydroxide obtained through extraction processing of rare-metal-containing raw materials. The phase composition of Nb2O5〈Dy〉 precursors was determined by X-ray diffraction and IR spectroscopy. Using inductively coupled plasma mass spectrometry in combination with a laser ablation sampling system, we examined the Dy dopant profile in Nb2O5 powder samples and the LiNbO3 growth charge. The Nb2O5 precursors and the growth charge synthesized using them were shown to be chemically uniform in composition. The present results are of importance for the growth of defect-free lithium niobate single crystals of optical quality, highly uniform in composition, with a predetermined doping level.

An effect of nature and concentration of a modifier on extraction of cobalt(II) from chloride solutions by trioctylamine

An effect of modifiers on extraction of cobalt from chloride solutions was studied in an extraction mixture with trioctylamine. An optimal range of concentration of the most active modifier, actanone-2, was up to 50%. Excess concentrations of octanone-2 led to structural changes and reduced ketone extraction of cobalt.

Synthesis of Nb2O5〈B〉 solid precursors and LiNbO3〈B〉 batches and their phase compositions

A process has been developed for preparing boron-doped niobium pentoxides Nb2O5〈B〉 to be used as precursors in the sysnthesis of nithium biobate batches LiNbO3〈B〉 having tailored dopant concentrations. Solutions of various origins were used to isolate Nb2O5〈B〉. A method has been advanced to account for boron loss as volatile compounds upon the heat treatment of niobium hydroxide in order to determine the boron amount to be added to niobium hydroxide in the form of H3BO3. The boron concentration in LiNbO3〈B〉 during lithium niobate synthesis is shown to be independent of the origin of the Nb2O5〈B〉 precursor with the same as-batch boron concentration. The phase compositions of Nb2O5〈B〉 and LiNbO3〈B〉 have been characterized by X-ray powder diffraction and IR spectroscopy and boron concentrations have been determined for the synthesis of single-phase lithium niobate batches for use in the production of optically uniform single crystals and pore-free piezoelectric ceramics.

Physicochemical simulation of calcite (dolomite)-FeSO4-H2O open systems

Effect of the chemical composition of carbonate minerals on the precipitation of iron from a Fe(II) sulfate solution was studied.

Physicochemical properties of phosphate extracts and mutual solubility of phases in the extraction system with monofunctional aliphatic alcohols

The main physicochemical properties of the extracts, such as density, viscosity, and conductivity, as well as the mutual solubility of the phases in the ROH-H2O and ROH-H2O-H3PO4 extraction systems, where ROH (R = C5–C10) stands for higher monofunctional aliphatic alcohols with a different length and structure of the hydrocarbon radical, have been studied in water and aqueous solutions containing phosphoric acid. The properties correlate with the length and structure of the hydrocarbon chain in the aliphatic alcohols, as well as with the concentration of mineral acid in the extracts.

Preparation of concentrated alkali solutions of niobium

Concentrated alkali solutions of niobium containing up to 238 g/L of Nb2O5 have been obtained by sintering of Nb2O5 with K2CO3 · 1.5 H2O. These solutions are recommended for use in the production of welding and other functional materials.

Synthesis and investigation of homogeneously doped precursor Ta2O5〈Sm〉 and charge of composition LiTaO3〈Sm〉

For growing single crystals of lithium tantalate of optical quality with high homogeneity of their composition and desired concentration of dopant of samarium a method for producing a solid precursor Ta2O5〈Sm〉 and homogeneously doped charge LiTaO3〈Sm〉 of a congruent composition was developed. X-ray diffraction analysis and IR spectroscopy were used to study the phase composition of Ta2O5〈Sm〉 and LiTaO3〈Sm〉. Conditions for preparation of the monophasic charge LiTaO3〈Sm〉 were determined: (Sm concentration in Ta2O5 ≤ 1.5 wt %, the molar ratio [Li2O]/[Ta2O5] = 0.941, synthesis temperature 1200°C). By mass spectrometry with inductively coupled plasma and sampling by laser ablation a distribution of the dopant of samarium in Ta2O5〈Sm〉 and LiTaO3〈Sm〉 was examined and the chemical homogeneity of the synthesized products was confirmed.

Preparation and phase composition of Ta2O5:Zn alloys having low Zn2+ concentrations

Methods were developed for preparing Ta2O5:Zn alloys containing less than 3 wt % Zn2+ for the purpose of using them further in preparing lithium tantalate batches and growing from them single crystals having improved properties. A method where zinc is doped directly into a tantalum-containing back-extract followed by precipitation of tantalum and zinc hydroxides with ammonia is confined to a Zn2+ concentration of 1.7 wt % in Ta2O5; at higher concentrations, Zn2+ forms soluble ammine complexes. A method where Zn2+ is extracted by high-purity tantalum hydroxide is applicable within the range of Zn2+ concentrations studied. Optimal conditions were found for preparing Ta2O5:Zn2+ alloys of various compositions. X-ray powder diffraction and IR spectroscopy were used to study the phase composition of the alloys synthesized, and Zn2+ concentrations were determined at which a ZnTa2O6 phase was formed along with the major Ta2O5 phase.

Synthesis and research of phase composition of alloys Nb2O5: Fe3+ and Ta2O5: Fe3+

The conditions were studied for the synthesis of niobium and tantalum pentoxide containing iron impurity introduced into the strip liquor after extraction separation of niobium and tantalum and subsequent precipitation of metal hydroxides with ammonia. A phase composition of the synthesized alloys was examined by X-ray diffraction and infrared spectroscopy.

On potassium hexaniobates released in the course of preparation of concentrated niobium(V) alkaline solution

Solutions containing 500 g L−1 Nb2O5 were obtained by sintering Nb2O5 with potash followed by leaching with water. The potassium niobate released from niobium(V) alkaline solutions was examined with an application of methods of physical and chemical analysis. Hydrates K8Nb6O19·4H2O and K7.5[H0.5Nb6O19]·14H2O were first obtained.