6 It is also used in high-voltage capacitors. It has a specific resistivity of over 10 9 -cm for very pure crystals. deposited at the same substrate temperature but with the other conditions not optimal (at a lower r.f. Synthetic strontium titanate has a very large dielectric constant (300) at room temperature and low electric field. The effective mass depends on ordering, namely on the distance of the foreign atoms. XRD spectra: curve a, SrTiO3 powder: curve b, SrTiO3 film deposited onto MgO at 600. While the effective masses for the metallic and the semiconducting compositions were less than 0.5, the effective mass near the MIT was around m*/m0 = 9 for SrNb0.2Ti0.8O2.98. The temperature dependence of the lattice constant of SrTiO3, in particular around the 106 K transition, has been measured by using a double-crystal X-ray. The goal of this investigation is to clarify which ordering state is expected to have the higher Seebeck coefficient by estimating the effective mass from ab-initio band structure calculations, as successfully applied for Nb-doped SrTiO3 and metallic alloys. Experimental data on PbTe2-AgSbTe2-solid solutions near the metal-insulator- transition (MIT) showed controversy resulting in high or low values of the Seebeck-coefficient and could partly be explained by specimen inhomogeneties and resulting measurement difficulties or different ordering states.
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