Studies were carried out to reduce the leakage current of high-voltage ZnO varistor ceramics by varying Sb2O3 and NiO content in a ZnO-Bi2O3-Sb2O3-Al2O3-Co3O4-NiO. It was found that the ceramic composition (wt %): ZnO 80, Bi2O3 5.83, Sb2O3 2.62, A12O3 4.66, Co2O3 3.80, NiO 3.09, has a minimum leakage current density Iout ≤ 0.1 μA cm-2, breakdown voltage Ub = 4.1kV mm-1, nonlinearity coefficient α = 65. The resulting ceramics are promising for the production of varistors with high stability of performance.

— This paper presents a study aimed at determining the weight ratio of oxide additives for obtaining high-voltage ceramics in the ZnO–Bi 2 O 3 –Sb 2 O 3 –Al 2 O 3 –Co 3 O 4 system containing 90 wt % ZnO, with a leakage current density under 1 μA/cm 2 . The ceramic containing the oxide additives in the ratio Bi 2 O 3 : Sb 2 O 3 : Al 2 O 3 : Co 3 O 4 = 0.25 : 0.17 : 1.4 : 1.4 has a nonlinearity coefficient as high as α = 69, a leakage current density as low as I l = 0.4 μA/cm 2 , and a breakdown voltage V b = 4.1 kV/mm.

Varistor powders were synthesized by accelerated combustion of an aqueous solution of hydrated zinc, bismuth, aluminum, cobalt, and nickel nitrates, antimony tartrate, and sugar at 500°С with isothermal heating for 10 min, followed by grinding and calcination at 700°С for 1 h. The varistor powders obtained have high specific surface area and allow preparation of a ceramic with high values of the breakdown voltage and nonlinearity coefficients and with low leakage current density. The ceramic of the optimum composition (wt %), ZnO 75, Bi2O3 7.36, Sb2O3 5.1, Al2O3 7.19, Co2O3 4.8, and NiO 0.61, sintered at 975°С for 4 h, has U b = 4.2 kB mm–1, α = 54, and I leak = 0.2 μA cm–2.

This paper presents a study aimed at optimizing the composition and sintering conditions of highvoltage ZnO varistor ceramics. We demonstrate that, with allowance for the cost of starting materials, the optimal composition of high-voltage ZnO varistor ceramics is as follows (wt %): ZnO, 90; Bi2O3, 2.76; Sb2O3, 1.92; Al2O3, 3.32; and Co2O3, 2. The optimal sintering conditions are isothermal holding at a temperature of 975°C for 2 h. The ceramics thus prepared have V b = 4.5 kV/mm, α = 50, I l = 1.1 μA/cm2, density ρ = 5.67 g/cm3 (relative density of 96.1%).

We have examined the effect of dopant concentration on the properties of ZnO varistor ceramics and determined the composition and conditions of the synthesis of ceramic powders and sintering of ceramics at a temperature of 925°C. We obtained a breakdown voltage of 2.8–3.0 kV/mm and nonlinearity coefficient in the range 48–55.

Исследован процесс получения электродного материала LiCoPO4, модифицированного литийпроводящим твердым электролитом состава Li1.3Al0.3Ti1.7(PO4)3 (LATP). Для создания композита, состоящего из электрохимически активного вещества и электропроводной добавки, равномерно распределенной между частицами LiCoPO4, использовали пероксидный раствор-прекурсор LATP. После прокаливания при 700°C получен двухфазный композит LiCoPO4/LATP с проводимостью на 2 порядка выше исходной проводимости двойного фосфата лития-кобальта при комнатной температуре.

A modified sol-gel process was studied as applied to synthesize a lithium-conducting solid electrolyte of composition Li1.3Al0.3Ti1.7(PO4)3 (LATP) using water-soluble salts Al(NO3)3 · 9H2O, LiNO3 · 3H2O, and (NH4)2HPO4 and a titanium(IV) citrate complex. As-synthesized samples were characterized using X-ray powder diffraction, DSC/TG, SEM, and impedance spectroscopy. Sintering of as-synthesized amorphous powders at 700°C was found to yield LATP with crystallite sizes of 42–48 nm. Ionic conductivity of the electrolyte measured in the frequency range 25–106 Hz in disks having 86–90% density that were sintered at 1000°C was (3–4) × 10−4 S/cm. Temperature-dependent ionic conductivity was studied in the range 25–200°C. The activation energy of conduction was determined for LATP.

The process for producing the electrode material LiCoPO 4 modified by the lithium-conducting solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) was studied. To create a composite consisting of an electrochemically active substance and an electrically conductive additive distributed uniformly between LiCoPO 4 particles, a peroxide solution of a LATP precursor was used. After annealing at 700°C, the two-phase composite LiCoPO 4 /LATP was obtained, the conductivity of which was two orders of magnitude higher than that of binary lithium cobalt phosphate at room temperature.

It was found in using anatase titanium oxide for the preparation litium hexafluorotitanate by interaction of titanium hydroxide or oxide and lithium fluoride with hydrofluoric acid an output of Li2TiF6 reached 97.1% at “reverse” synthesis, 100% consumption of LiF and 200% consumption of 54% HF.

The decomposition of silver selenide and sulfide to metallic silver and chalcogen containing oxygen compounds by sintering with an equimolar mixture of sodium nitrate and nitrite was examined. It was found that 100% recovery of silver in a metal phase is reached at 5% excess of sodium nitrate and nitrite and a time of the isothermal exposure at 375 °C 1 hour or half an hour at 400°C.

The synthesis of ZnO:Ga(0.075 wt%) nanosized powders via combustion reaction at 145°C and subsequent calcination of the ground combustion product at 500–900°C was studied. Zinc and gallium nitrates were used as initial substances, and sucrose, as fuel. It was found that Ga 2 O 3 nanoparticles are located on the ZnO particles and inhibit their growth.

Synthesis of MgAl2O4 from a stoichiometric mixture of aluminum and magnesium nitrates by its burning with urea, glycine, sugar, and mixtures of these as a fuel was studied.

This paper describes a process for the preparation of powders and films of the lithium ion conducting solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 from peroxide solutions. The use of peroxide solutions ensures the preparation of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 with a room-temperature electrical conductivity of (4–5) × 10 −4 S/cm by calcining a precursor at 800°C. The synthesized Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 powders were characterized by X-ray diffraction, thermal analysis (DTA/TG), and ionic and electronic conductivity measurements. The growth of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 solid electrolyte films is described.