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FEATURES OF THE ELECTROPHYSICAL PROPERTIES OF DOPED LAYERED OXYMOLYBDATES (PbO)x(Ln2MoO6)(1-x)/2 (Ln=La,Nd) AND FLUORITE-LIKE OXYFLUORIDES МeLn4Mo3O15F (Me=Li,Na,K)тезисы доклада
- Авторы: Voronkova V.I., Kharitonova E.P., Orlova E.I.
- Сборник: Conference Proceedings 14th International Conference Fundamental Problems of Solid State Ionics, Chernogolovka, Russia, 9-13 September, 2018
- Тезисы
- Год издания: 2018
- Первая страница: 292
- Аннотация: Several molybdates of nearby composition were found while studying of Ln2O3-MoO3 systems: fluorite-like cubic Ln5Mo3O16 compounds (5:6) with mixed electron-ion conductivity of interstitial type [1], and Ln2MoO6 oxymolybdates (1:1), which conductivity has been studied insufficiently. The structure of rare-earth Ln2MoO6 (Ln = La, Pr, Nd) oxymolybdates is tetragonal, layered, constructed of two fluorite layers and a layer of isolated tetrahedra [2]. A feature of the cubic structure of fluorite-like compounds Ln5Mo3O16 was the existence of isolated Mo tetrahedra near sufficiently large voids. The purpose of this work was to reveal the effect of doping of oxymolybdates and fluorite-like compounds on their physical properties. It was found that a wide range of (PbO)x(La2MoO6)(1-x)/2 solid solutions with a layered tetragonal structure is formed in the Ln2MoO6–PbO system by lead doping. The range of solid solutions was 0≤x≤0.34 for Ln = La and 0≤x≤0.6 for Ln = Nd. Doping with lead resulted in an unusual effect, the appearance of a superionic reversible phase transition. This transition was observed at 820 °C for compounds with Nd and at 775 °C with La. The existence of this transition was confirmed by DSC and electrophysical measurements. At the temperatures indicated above, a superionic jump in the conductivity by two orders of magnitude and a dielectric anomaly of the ferroelectric type were observed. In oxyfluorides MeLn4Mo3O15F a phase transition of the ferroelectric type with a jump in the electrical conductivity by 2 orders of magnitude also arises in the region of 600-800 °C. It can be assumed that the appearance of a phase transition and a radical change in the electrophysical properties of rare-earth doped oxyfluorides and oxymolybdates may be due to weak structural changes, which are not detected by powder XRD methods. References: 1. M. Tsai, et al // Chem. Mater. 1989. V. 1. P. 253–259. 2. V.A. Efremov at al. Koordinatsionnaya Khimiya. 13 (1987) 1276.
- Добавил в систему: Воронкова Валентина Ивановна