Lattice dynamics and dielectric response of Mg-doped SrTiO3 ceramics in a wide frequency range
authors Tkach, A; Vilarinho, PM; Kholkin, AL; Pashkin, A; Samoukhina, P; Pokorny, J; Veljko, S; Petzelt, J
nationality International
journal JOURNAL OF APPLIED PHYSICS
keywords TUNABLE MICROWAVE APPLICATIONS; THIN-FILMS; ELECTRIC-FIELD; STRONTIUM-TITANATE; PHASE SHIFTERS; BEHAVIOR; TEMPERATURE; DEPENDENCE
abstract Atomic substitutions in the SrTiO3 (ST) perovskite lattice are foreseen to modify the lattice vibration modes, which are apparently sensitive to the site at which the substitution occurs. In order to understand the effect of Mg substitution in the ST lattice, the dielectric properties of Sr1-xMgxTiO3 and SrTi1-yMgyO3-delta ceramics were investigated in radio frequency (rf), microwave, terahertz (THz), and infrared (IR) ranges. Micro-Raman spectroscopy and rf tunability measurements were also conducted on these samples. The micro-Raman spectra and the high-frequency dielectric properties of Sr1-xMgxTiO3, including rf tunability, do not differ considerably from the properties of undoped SrTiO3, confirming only slight (if any) incorporation of Mg into the Sr site of ST perovskite lattice. At the same time, Ti-site Mg doping results in significant stiffening of the soft lattice mode observed in IR reflectivity spectra. Dielectric permittivity and dielectric losses decrease in both rf and THz ranges accompanied by the decrease of the tunability, in accordance with the stiffened ferroelectric soft mode. The appearance in the Raman spectra of the forbidden polar modes TO4 at 545 cm(-1) and TO2 at 174 cm(-1) at room temperature and their strengthening on cooling, demonstrate the local loss of the inversion center and the breaking of the cubic symmetry by the substitution of Ti4+ by Mg2+ ions. These results confirm more favorable occupation of Mg at the Ti site of the ST lattice and show the possibility of using Ti-site Mg-doped ST as an active material for low-loss microwave waveguides and resonators. (C) 2005 American Institute of Physics.
publisher AMER INST PHYSICS
issn 0021-8979
year published 2005
volume 97
issue 4
digital object identifier (doi) 10.1063/1.1849822
web of science category Physics, Applied
subject category Physics
unique article identifier WOS:000226841900063
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