Dielectric relaxations of charge-ordered Ln 1.5 Sr 0.5 NiO 4 ( Ln = La and Nd) ceramics were investigated over a broad temperature range. The giant dielectric constant (over 70 000 ) with a low dielectric loss of ∼0.1 was determined at high frequencies (up to 5 MHz) over a broad temperature range. There are two dielectric relaxations in the vicinity of charge ordering temperatures. The thermal activated small polaronic hopping between two charge ordering temperatures should contribute to the giant dielectric response in the present ceramics. Compared to other giant dielectric constant materials, the present materials have the notable advantage for high frequency applications.
[Show abstract][Hide abstract] ABSTRACT: Many transition-metal oxides show very large (“colossal”) magnitudes of the dielectric constant and thus have immense potential
for applications in modern microelectronics and for the development of new capacitance-based energy-storage devices. In the
present work, we thoroughly discuss the mechanisms that can lead to colossal values of the dielectric constant, especially
emphasising effects generated by external and internal interfaces, including electronic phase separation. In addition, we
provide a detailed overview and discussion of the dielectric properties of CaCu3Ti4O12 and related systems, which is today’s most investigated material with colossal dielectric constant. Also a variety of further
transition-metal oxides with large dielectric constants are treated in detail, among them the system La2−xSrxNiO4 where electronic phase separation may play a role in the generation of a colossal dielectric constant.
The European Physical Journal Special Topics 12/2010; 180(1):61-89. DOI:10.1140/epjst/e2010-01212-5 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this work is to improve the dielectric properties of giant permittivity La1.5Sr0.5NiO4 ceramics. The microstructure and dielectric properties of Ga‐doped La1.5Sr0.5NiO4 ceramics prepared by a solid state reaction method were investigated. It was found that Ga3+ doping ions have a remarkable influence on the microstructural evolution. La1.5Sr0.5Ni1 − xGaxO4 (x = 0, 0.1, and 0.3) ceramics exhibited giant dielectric constant with ε′ ~ 3.3–4.7 × 105 at 20 °C and 1 kHz. Interestingly, ε′ of La1.5Sr0.5Ni1 − xGaxO4 ceramics was enhanced by doping with Ga3+; whereas, the loss tangent (tanδ) decreased significantly. Reduction of tanδ is attributed to the increase in the total resistance, which is mainly governed by the sample–electrode contact resistance, and caused by a decrease in dc conductivity.
[Show abstract][Hide abstract] ABSTRACT: The crystalline structure and dielectric properties of nominal Sm 1.75 Sr 0.25 NiO 4 ceramics are presented. Three phases, Sm 1.70 Sr 0.30 NiO 4 , Sm 2 O 3 and NiO, are found in the present ceramics, and the abundances are 77.7(1.1) wt%, 19.2(3) wt% and 6.1(2) wt%, respectively. The temperature-stable giant dielectric constant over 60 000 even up to 5 MHz is observed in a broad temperature range. The modulus plots show that the giant dielectric constant should be originated from the contribution of the grain interior instead of grain boundary. Compared with the other giant dielectric constant materials, the present materials have the great potentiality in the practical application, especially for the high frequency application.
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