کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
7990300 1516127 2018 30 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
High dielectric constant and relaxor behavior in La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 manganite
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد فلزات و آلیاژها
پیش نمایش صفحه اول مقاله
High dielectric constant and relaxor behavior in La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 manganite
چکیده انگلیسی
The dielectric properties of La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 (LSNMTi0.2) were investigated as a function of temperature and frequency. Compared with the dielectric constants of most ferroelectric and relaxor materials, in this compound we have found a colossal dielectric constant phenomenon consisting in a low frequency dielectric constant ε″ over 106 around room temperature. However, Frequency and temperature dependent ac conductivity and complex impedance studies were linked to semiconducting grains and insulating grain boundaries, which support the non-Debye type of relaxation in the polycrystalline sample. Furthermore, decrease in the resistive properties with an increase in temperature, explained in terms of the mobility of the charge carriers, signaled the semi-conductor behavior with negative temperature coefficient of resistance (NTCR). The scaling behavior of the Modulus spectra M″ versus frequency allowed us to understand whether the short-range or the long-range movement of charge carriers is the dominant in relaxation process, confirming the non-Debye type of multiple relaxations in the system. The variation in the dielectric permittivity, explained in terms of the space charge polarization according to the Maxwell-Wagner model and the Koop's phenomenological theory and the large dielectric response, was induced by the barrier layers in the grain boundaries and the mixed-valent structures of Mn3+/Mn4+ and Ti4+/Ti3+.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Alloys and Compounds - Volume 767, 30 October 2018, Pages 456-463
نویسندگان
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