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Mashkina Nataliya Viktorovna

Theme of master's work:

Ecologically safe synthesis and nature of oxygen unstoichiometry in cuprat YBa_1,94Sm_0,06Cu_2,995Li_0,005O_X

The scientific leader: PRISEDSKIY VADIM VIKTOROVITCH

The theme actuality

    Materials on the basis of high temperature superconductors (HTSC) oxides are very perspective for application in different areas of modern electronic technique. However, problems related to ecological safety and labour protection during the production of oxide superconductive materials remain not decided.

    Lately considerable attention during the study of oxide HTSC is taken by the researches of influence of heterovalency substitutions of cations in the structure of RBa₂Cu₃O_x. It was before exposed, that in a number of cases heterovalency substitutions in a structure can pretty substantially influence both – the state and the maintenance of oxygen and electro-physical properties of phase 123. But presently the number of such conducted researches is extremely not enough for the creation of experimental information base, on the basis of which it would be possible to forecast properties of the modified phases of type 123.

Purpose and research tasks

    The research purpose lies in the realization of ecologically safe method of synthesis of ceramic cuprat barium-yttrium alloyed by samarium in practice and the study of its oxygen unstoichiometry features.

    Tasks, decided in master's degree work:

    1. Analysis of the question state and study of literary sources on the features of oxygen unstoichiometry of high temperature superconductors.

    2. Realization in practice ecologically safe method of synthesis of ceramic cuprat barium-yttrium, alloyed by samarium.

    3. Conducting of thermocycling of the explored standard in the temperature range of 20-900⁰C in the open air, using the gravimetrical setting.

    4. Construction of cooling and heating curves, which give the picture of oxidization and renewal of standard on the rapid and slow constituent of oxygen unstoichiometry.

    5. On the basis of the conducted gravimetrical researches to draw conclusion about the influence of heterovalency substitution of barium positions by the samarium atoms on oxygen consisting of superconductive cuprat composition of YBa_1,94Sm_0,06Cu_2,995Li_0,005O_X.

Scientific novelty and practical value

    Taking into account the fact that problems related to ecological safety and labour protection during the production of oxide superconductive materials remain not decided, in this work ecologically safe method of synthesis of ceramic cuprat was offered and realized in practice.

    Also in this work the researches of influence of heterovalency substitution of barium positions by the samarium atoms on oxygen consisting of superconductive cuprat composition of YBa_1,94Sm_0,06Cu_2,995Li_0,005O_X.

    The practical value consists in the fact that the findings make physical and chemical basis for the receipt of HTSC with the controlled chemical composition and set properties. The results of research of equilibrium maintenance of oxygen and its influence on a structure and properties are initial at the construction of models of superconductivity and criteria choice of new classes of HTSC research.

Results and their discussion

    The study of oxygen maintenance change during the thermocycling standard of YBa_1,94Sm_0,06Cu_2,995Li_0,005O_X in the temperature range of 20-900°C in the open air was conducted on the gravimetrical setting (figure 1), allowing to register mass in the heat treatment process continuously.

Figure 1 - Gravimetrical setting (5 slides with an interval 1 seconds, unlimited number of recurrences)

    The results of the conducted researches showed that over alloying of cuprat barium-yttrium a samarium brought to introduction in the crystalline grate of additional amount of oxygen.

    The experimental findings confirmed the pre-established fact that standards of cuprat barium-yttrium, alloyed by samarium, show two types of oxygen unstoichiometry, which differ by connection energy and diffusion speed in a crystalline grate. Conventionally they were named as «rapid» and «slow» constituent of oxygen unstoichiometry.