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Samples of lanthanum lithium titanate with the general formula La 2/3 -x Li 3x TiO 3 with a different vacancy content, which is varied by varying the ratio of lanthanum to lithium, are investigated. Methods of synthesis, neutron diffraction data for the samples obtained, measurements of the lithium-ion conductivity of equilibrium and quenched samples, the results of nuclear magnetic resonance on 7 Li nuclei, the dynamic characteristics of heat release (heat absorption), and the magnetic susceptibility of some samples are presented.Materials based on lanthanum lithium titanate with perovskite structure have been studied intensively for the last 10 years in virtually all industrially developed countries. Being purely ionic conductors with respect to lithium they are drawing the attention of researchers primarily because these conductors have unique electric properties, making them promising as separators of low-and medium-temperature lithium sources of electric current. The conductivity of samples of materials with the general formula La 2/3 -x Li 3x TiO 3 (LLTO) depends strongly on the ration of lanthanum and lithium, since this ratio determines the concentration of cationic vacancies. In a series of works [1 -3] the formula for the compound is written in the form La 2/3 -x Li 3x 1/3 -2x TiO 3 , where the symbol denotes a cationic vacancy, showing this dependence directly. For x~0.1 the compound at room temperature has a lithium-cationic conductivity of approximately 10 -3 S/cm [1,2]. In practice, this is the highest ionic conductivity known today at these temperatures in crystalline bodies. The electronic conductivity of materials in air is so low that it cannot measured within the limits of sensitivity of modern instruments.Materials based on LLTO possess high ceramic characteristics: they press well and sinter at 1200 -1300°C. This makes it possible to miniaturize devices which are manufactured using LLTO materials. Articles made from raw materials with a low content of cationic impurities with variable valence have a dull white color.The present article presents the results of investigations of the effect of the structural and thermal properties and the cooling regimes of the samples on the ionic conductivity of LLTO. To this end the samples were obtained under equilibrium conditions or quenched in air and liquid nitrogen.The samples were synthesized using the well-known ceramics technology [1,2]. Calcined powders served as the initial materials: chemically pure La 2 O 3 , pure TiO 2 , and chemically pure Li 2 CO 3 . Weighed batches were mixed in an agate mortar, pressed at pressure 200 -220 MPa into 13 mm in diameter and 3 -5 mm thick pellets. The pellets were placed into a corundum crucible and a Silit furnace. Synthesize was conducted in air in four stages. At the first stage the samples were calcined at 900°C for 9 h. After cooling they were ground and pressed once again under the same pressures. Subsequent calcinations were performed at 1200°C for 24 h with intermediate millings of the materials. The fina...

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Unit Cell, Phase Transition, and Electrical Conductivity of LaYO 3 . -LaYO 3 , obtained by annealing the corresponding oxides at 1300-1500 • C, appears to be a pseudocubic phase, ordered based on a perovskite mode with monoclinic unit cell (Z = 64). A high-temperature phase transition of the type order-disorder, affirmed by a change of electric conductivity, is observed at 1505 • C. -(GORELOV, V. P.; MARTEM'YANOVA, Z. S.; BALAKIREVA, V. B.; Neorg. Mater. 35 (1999) 2, 208-212; Inst. vysokotemp. elektrokhim., Ural. otd. Ross. Akad. nauk, Ekaterinburg, Russia; RU)

It is shownthat fully sintered ceramic mixtures for floor tile can be obtained from Berlinclay with additionof pegmatitefrom the Chupinskoe and Vishnevogorskoe deposits. The phase composition and microstructure of the synthesized materials are described.In Russia, ceramic floor tile is produced in correspondence with the requirements of GOST 6787-90 State Standard. The water absorption of the tile should not exceed 4%. At the present time, the building industry demands floor tile without open porosity and with zero water absorption. Such tile possesses high technical characteristics and can be polished, which improves considerably the appearance of the structures.As a rule, ceramic tile for floors is produced from mixtures that contain 80% plastic components and 20% fluxes (here and below in mass fractions) [1,2]. In order to obtain fully sintered ceramic mixtures, we studied compositions with a much higher content of fluxes (50 -70%).The ceramics industry does not use mixtures with such a high flux content, because in addition to the positive sintering action, the fluxes can have a negative effect, i.e., increase the susceptibility of the products to deformation and increase the closed porosity.We tested the raw components used by the Ekaterinburg Ceramic Plant, namely, Berlin clay and Chupinskoe and Vishnevogorskoe pegmatite. The chemical composition of these materials is presented in Table 1.We began with a study of some properties of the initial components. The properties of Berlin clay were studied in [3]. The thermogram of the Berlin clay obtained by us is presented in Fig. 1.In deciphering the DTA data, we established that the predominant clay mineral is kaolinite (the endothermic effect at 578°C caused by removal of chemically bound water from the kaolinite and the exothermic effect at 940°C connected with rearrangement of the metakaolinite lattice).The Berlin clay also contains montmorillonite (endothermic effect of removal of adsorption water at 185°C). Our 119 data on the mineralogical composition of the Berlin clay coincide with the results of [3]. i.e., the Berlin clay has a kaolinite-montmorillonite composition. We used the method in [4] for calculating the activation energy of the process of removal ofadsorption water, which amounted to 28 kJ Imole, and the energy of removal of chemically bound water from kaolinite, which was 89 kl/mole, Berlin clay belongs to the medium-plastic category. The picnometric density of the clay in the natural state is 2.53 g/cm 3 • The clay is moderately sinterable at a moderate temperature.In order to determine the heating behavior of Vishnevogorskoe and Chupinskoe pegmatites, these materials were preliminarily crushed (no residue on screen T Fig.