Giant dielectric response in two-dimensional charge-ordered nickelate ceramics
ABSTRACT 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.
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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.Ferroelectrics. 01/2009; 388(1):161-166.