— An yttrium ammonium carbonate with the composition NH 4 Y(CO 3 ) 2 ∙ H 2 O has been prepared by reacting hydrated yttrium oxide with ammonium carbonate at 80°C. The synthesis process has been shown to proceed through crystallization of two intermediate phases: yttrium ammonium hydroxycarbonates differing in composition. The synthesized compounds have been characterized by X-ray diffraction, IR spectroscopy, differential scanning calorimetry, thermogravimetry, and chemical analysis. The first X-ray diffraction characteristics of NH 4 Y(CO 3 ) 2 ∙ H 2 O and crystallographic data for its unit cell have been presented. Thermal decomposition of the yttrium ammonium carbonate has been shown to yield cubic yttrium oxide in the form of fine powder.

We have studied the effect of precursors on the synthesis conditions and characteristics of molybdenum nitrides. Mo, MoO3, and MgMoO4 powders were nitrided in flowing ammonia at temperatures in the range 500–800°C. The use of molybdenum nanopowder as a precursor has made it possible to reduce the synthesis temperature and time. We have demonstrated the possibility of direct ammonolysis of the double oxide MgMoO4. Using this molybdate, we have obtained a material with a specific surface area up to 29 m2/g, which is a factor of 2 to 3 larger than that reached by nitriding MoO3. In all cases, the synthesis products consisted of the γ- and β-phases of Mo2N, with cubic and tetragonal lattices, respectively.

The phases NdF3 (I), x (II), NdTi2O4.75F0.5(SO4)0.5 · 3H2O (III), NdTiF3(SO4)2 · 6H2O (NdTiOF(SO4)2 · 6H2O) (IV), Nd2(SO4)3 · 8H2O (V), and Nd2(SO4)3 · 4H2O (VI) formed in sulfuric acid and fluorine-containing solutions during the synthesis of materials from feedstocks and the purification and separation of metals were separated. The regions of their existence were schematically presented. Particles with a “core-shell” structure were detected. The compounds were studied by elemental, crystallooptic, X-ray diffraction, and thermal analyses. The composition was determined for phase III (from thermogravimetric (TG) data) and spherolith-like particles of H6NdF7.8(SO4)0.5 · 3.75H2O (VII) (by X-ray diffraction microanalysis). Freshly separated particles evolved HF. Phase IV corresponding to NdTiF3(SO4)2 · 6H2O (according to TG data) acquired the composition and form of the known NdTiOF(SO4)2 · 6H2O phase after storage.

We have studied the feasibility of preparing tantalum and niobium nitrides by reducing Та2O5, Nb2O5, Mg4Та2O9, and Mg4Nb2O9 with magnesium vapor. The process was run in two steps: (1) reduction of the oxides at a temperature of 820°C and a residual argon pressure of 5 kPa in the reactor for 4 h and (2) nitridation of the reduction products in a nitrogen atmosphere at 820 and 900°C for 1–12 h. The phase composition of the powders after leaching out the magnesium oxide was determined on DRF-2 and DRON-4 X‑ray diffractometers. The specific surface area was determined by BET adsorption measurements on a Micromeritics TriStar II 3020 analyzer. When Ta2O5 was used as precursor, the nitridation product contained θ-TaN, ε-TaN, and Ta2N. The use of Nb2O5 as a precursor led to the formation of face-centered cubic NbN, hexagonal close-packed NbN, Nb2N, and Nb4N3. The Mg4Ta2O9 and Mg4Nb2O9 reduction products did not absorb nitrogen. The results obtained are discussed in detail.

The solubility was studied for compounds in the system Zr(SO4)2–K2SO4–H2SO4–H2O in the section at 10 wt % H2SO4 under isothermal conditions at 25°C in the cuts at a constant solvent content of 60 wt % (H2O + H2SO4). Equilibrium in the system was reached for 16 h while continuously stirring. In the section at 10 wt % H2SO4, equilibrium solid phases are the compounds K2Zr(SO4)3 ⋅ 2H2O, K3Zr(OH)(SO4)3 ⋅ 2H2O, K6Zr(SO4)5 ⋅ 3H2O, and β-K2SO4. The recovered compounds were investigated by X-ray powder diffraction, crystal optical, thermal analyses and IR spectroscopy. It was found that the solubilities of the potassium zirconium sulfates are much lower than those of the sodium zirconium compounds. The results are of practical importance for sulfuric acid treatment of eudialyte, a zirconium-containing mineral, huge reserves of which occur in the Kola Peninsula.

Tantalum nitrides are synthesized by ammonolysis of a mesoporous magnesiothermic tantalum powders. The effect of specific surface area of the powders and synthesis temperature on product composition is shown. Nitrogen content in the ammonolysis product of tantalum powder with a specific surface area of 56 m2 g–1 corresponds to oxynitride TaON exposed to 600°C for 1 h. The specific surface area of the oxynitride is 35 m2 g–1.

Effect of the solution redox potential on the behavior of cobalt-containing phase components of sulfide copper-nickel concentrates in the Cu(II)/Fe(III)–Cl––HCl–Cl2 system was studied. It was shown that, at solution redox potentials in the range 350–650 mV, phases based on heazlewoodite, pentlandite, cobaltous pentlandite, and cobalt pentlandite are transformed to thiospinels from the linneite group (M3S4, where M = Ni, Fe, Co). The resulting thiospinels are dissolved, with the exception of Co3S4, at solution redox potentials of 450 mV and less. The Co3S4 thiospinel is a stable compound in concentrated chloride solutions up to 650 mV, which, in the system under study, may be a reason for the poor cobalt recovery from sulfide concentrates.

Thermal decomposition of fluorooxalatozirconates (FOxZs) K 3 ZrF 5 C 2 O 4 , K 2 ZrF 4 C 2 O 4 ⋅ 2H 2 O, KZrF 3 C 2 O 4 ⋅ 3H 2 O, and Zr 4 O 3 F 2 (C 2 O 4 ) 4 ⋅ 2H 2 O in air flow is studied. Crystalline K 2 ZrF 4 C 2 O 4 and KZrF 3 C 2 O 4 are detected. The decomposition onset temperature of anhydrous products goes down as the K/Zr molar ratio decreases. Disproportionation of potassium FOxZs both at the oxalate group yielding K 2 ZrF 4 C 2 O 4 and ZrO 2– x /2 F x , K 2 C 2 O 4 and K 3 ZrF 7 and at fluorine yielding K 3 ZrF 7 and ZrO 2 takes place. FOxZs can be used as precursors to produce fine-grained ZrO 2 (baddeleyite).

The solubility in the quaternary water–salt system Zr(SO 4 ) 2 · 4Н 2 О–Na 2 SO 4 –H 2 SO 4 –H 2 O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na 2 SO 4 and Zr(SO 4 ) 4 · 4H 2 O, but also sodium sulfate zirconates Na 2 Zr(SO 4 ) 2 (OH) 2 · 0.3H 2 O, Na 4 Zr(SO 4 ) 4 · 3H 2 O, and Na 2 Zr(SO 4 ) 2 · 3H 2 O and two new compounds, S 1 and S 2 , which are presumably Na 2 ZrO(SO 4 ) 2 · 2H 2 O and Na 2 Zr 2 O 2 (SO 4 ) 3 · 6H 2 O.

Results obtained in studying the influence exerted by solution redox potential (360–600 mV), temperature (50–100°C), particle size (40–220 µm), and the initial concentrations of the chloride ion (1–6 M), hydrochloric acid 0–1.0 M), and copper(II) (0.08–0.39 M) on the behavior of the phase components of the copper–nickel matte in the course of leaching in the Cu(II)–Cl––HCl–Cl2 system.

The system ZrO(NO 3 ) 2 -H 2 C 2 O 4 -KF-H 2 O was studied in the sections C 2 O 4 2− : Zr = 1 and 2. The following compounds were isolated: crystalline fluorooxalate zirconates K 3 ZrF 5 C 2 O 4 , K 2 ZrF 4 C 2 O 4 · 2H 2 O, KZrF 3 C 2 O 4 · 3H 2 O, and KZr 2 (OH) 3 F 2 (C 2 O 4 ) 2 · 4H 2 O, and also oxofluorozirconate K 2 Zr 3 O 2.5 F 9 · 7H 2 O and oxofluoride oxalate Zr 4 O 3 F 2 (C 2 O 4 ) 4 · 2H 2 O. A crystalline phase and X-ray amorphous phases of undetermined compositions were detected. All the compounds, except K 2 ZrF 4 C 2 O 4 · 2H 2 O, were obtained for the first time; the crystals KZrF 3 C 2 O 4 · 3H 2 O, KZr 2 (OH) 3 F 2 (C 2 O 4 ) 2 · 4H 2 O, and K 2 Zr 3 O 2.5 F 9 · 7H 2 O were mechanically picked up from a mixture of phases. The composition KZr 2 (OH) 3 F 2 (C 2 O 4 ) 2 · 4H 2 O is conditional. The phases were identified by X-ray powder diffraction, crystal-optical, and elemental analyses, and also by X-ray microanalysis and IR spectroscopy.

Phase formation in the ZrO(NO3)2-NaF(HF)-H3PO4-H2O system was studied at 20°C and 2.0–14.5 wt % ZrO2 in the initial solution along sections with molar ratios PO 4 3− /Zr = 0.5 and 1.5 and also in the presence of hydrogen fluoride at Na/Zr = 1 and PO 4 3− /Zr = 0.5, 1.0, and 1.5. Crystalline zirconium hydrophosphate Zr(HPO4)2 · H2O, fluorozirconates Na5Zr2F13 and Na7Zr6F31 · 12H2O, fluorophosphatozirconates NaH2Zr3F3(PO4)4 · 3H2O and NaZr2F6(PO4) · 4H2O, and amorphous NaZrO0.5F(PO4) · 4H2O (provisional composition) were separated at room temperature. NaH2Zr3F3(PO4)4 · 3H2O and NaZr2F6(PO4) · 4H2O were prepared for the first time and were studied by crystal-optical, elemental, and thermal analyses, X-ray powder diffraction, IR spectroscopy, scanning electron microscopy (SEM), and X-ray microanalysis. Na7Hf6F31 · 12H2O was found to exist in a mixture with the hydrophosphate.

Co-Ni concentrates whose major phase components are pentlandite (Ni,Fe,Me) 9 S 8 , linneite Co 3 S 4 , polydymite Ni 3 S 4 , and siegenite NiCo 2 S 4 were subjected to oxidation with atmospheric oxygen under the conditions of nonisothermal and isothermal heating in the interval 20–900°C. The process was studied by differential thermal, X-ray phase, and chemical analysis. The reaction schemes based on the data obtained were suggested, and the optimal temperature interval of low-temperature sulfatizing roasting of Co-Ni thiosphinels was chosen.

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.

The phase formation in the system ZrO(NO 3 ) 2 -H 3 PO 4 -CsF-H 2 O was studied along the section at the molar ratios PO 4 3− /Zr = 1.5 and CsF/Zr = 2−5 at a ZrO 2 concentration in the initial solution of 2–5 wt %. New fluorophosphate zirconates, CsH 2 Zr 2 F 2 (PO 4 ) 3 · 1.5H 2 O and two modifications of CsZrF 2 PO 4 · 0.5H 2 O, were isolated, and the known phosphate zirconate CsZr 2 (PO 4 ) 3 was obtained for the first time by calcining acidic fluorophosphate zirconate.

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.

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.

The conditions for synthesizing tantalum pentoxide doped with magnesium oxide at the stage of the extraction separation of Ta2O5 were studied. The phase composition of the alloys synthesized was determined by the X-ray phase analysis and IR spectroscopy.