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Abstract
The structure, valence state, and dielectric properties of (Ba1−xSmx)(Ti0.99Mn0.01)O3 (BSTM) (x = 0.02‒0.07) ceramics prepared via a high temperature (1400 °C/12 h) solid state reaction were investigated. A homogeneous and dense microstructure was observed in all samples. With increasing Sm content, the crystal structure changed from tetragonal (x ≤ 0.06) to cubic (x = 0.07) and unit cell volume (V0) decreased continuously, which was mainly due to the substitution of Ba2+ ions by smaller Sm3+ ions in the perovskite lattice. Electron paramagnetic resonance investigation revealed that Mn ions were reduced from high valence to low valence under the role of Sm3+ donor, and only Mn2+ ions were observed at x = 0.07. The Curie temperature (Tc) moved to lower values, from 105.5 down to 20.4 °C, and the x = 0.07 sample satisfied Y5V specification with high permittivity (ε′RT > 13,000) and low loss (tan δ < 0.03).
Highlights
Transition metal Mn-doped BaTiO3 ceramics are widely applied in ceramic capacitors [1,2] and positive temperature coefficient of resistance (PTCR) devices [3,4]
Our study has found that hexagonal Ba(Ti0.97 Mn0.03 )O3 exhibits a low permittivity of about 100 at room temperature
Sm and Mn co-doped BaTiO3 ceramics with different Sm2 O3 contents, ranging from 2 to 7 at % Sm, were synthesized by a conventional solid-state reaction sintering at 1400 ◦ C in air for 12 h
Summary
Transition metal Mn-doped BaTiO3 ceramics are widely applied in ceramic capacitors [1,2] and positive temperature coefficient of resistance (PTCR) devices [3,4]. According to the earlier studies carried out in the air or in an oxidizing atmosphere, Mn is the most effective dopant for stabilizing hexagonal BaTiO3 (h-BT) at room temperature [10], and the existence of h-BT is attributed to the Jahn–Teller distortion (i.e., Jahn–Teller effect) caused by Mn3Ti+ [1] Such a structure is not desirable in the practical application of ceramic capacitors, since h-BT has a lower permittivity [11]. In Mn-doped BaTiO3 ceramics the partial replacement of Ba2+ by rare earth ions is reported to improve the dielectric properties and inhibit the formation of the undesired hexagonal phase. Besides the structure and dielectric properties of (Ba1−x Smx )(Ti0.99 Mn0.01 )O3 (BSTM), the valence states of Mn ions, which are closely related to the crystal structure, are discussed
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