Dependence of dielectric properties of manganese-doped strontium titanate ceramics on sintering atmosphere


It is shown in this paper that the microscopic mechanism of the dielectric relaxation in Mn-doped strontium titanate (SrTiO3-ST) ceramics is associated with the off-center displacement of Mn-Sr (2+) ions. This was accomplished by studying the dielectric properties and electron spin resonance spectroscopy in combination with X-ray powder diffractometry and scanning electron microscopy techniques in Srl-xMnxTiO3 ceramic samples sintered in different atmospheres (air, oxygen and nitrogen) at 1500 degrees C. First, it is shown that manganese is incorporated into the perovskite lattice of ST, preferably as Mn2+ at Sr sites. However, a small amount of Mn4+ at Ti sites is also observed when fired in air or oxygen flow. The concentration of Mn-Ti(4+) is the highest for sintering in oxygen, but firing in a reducing Ti atmosphere (nitrogen) results solely in the incorporation of Mn2+ at Sr sites. Correspondingly, the dielectric relaxation observed in Srl-xMnxTiO3 markedly increases in intensity and slightly shifts towards a higher temperature for ceramics sintered in nitrogen compared with those fired in air or oxygen. All these facts are consistent with a suggestion that the off-center displacement of Mn2+ ions at the Sr sites of the highly polarizable ST lattice is the source of the observed relaxation behavior. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.




Materials Science; Metallurgy & Metallurgical Engineering


Tkach, A; Vilarinho, PM; Kholkin, AL

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