To study the thermoelectric properties of SrTiO 3 doped with lanthanum and dysprosium, ceramic samples were prepared using the conventional solid-state reaction method. The total doping amount was fixed at 20 mol% with different amounts of lanthanum and dysprosium contents. The X-ray diffraction pattern suggests that the main crystal structure is cubic perovskite with a small amount of the second phase of Dy 2 Ti 2 O 7 . Scanning electronic microscope surface morphology images revealed that the ceramic samples consisted of homogeneous grains with an average grain size of 4.1-6.2 lm. The electrical conduction of the samples as a function of temperature had similar behavior to that of metallic conductivity. The Seebeck coefficients were negative, which indicates that electrons were the dominant carriers. As the dysprosium content increased, both the electrical conductivity and thermal conductivity decreased; in contrast, the absolute value of the Seebeck coefficient increased. The power factor reached 1318 lW/K 2 m at 570 K with 12% dysprosium and 8% lanthanum doped in SrTiO 3 . The lowest thermal conductivity was 2.3 W/mK for the sample with 20% dysprosium as a dopant. The maximum figure of merit (ZT) of 0.36 at 1076 K was obtained for SrTiO 3 doped with 12% dysprosium and 8% lanthanum, which is a result of the high power factor combined with low thermal conductivity.

Raman spectra of three bulk 4H-SiC wafers with different free carrier concentration were measured at temperature from 80 K to 873 K. As temperature increases, Raman peaks of most optical phonon modes show monotonous down shift. An anomalous non-monotonous variation with temperature, was observed in the A(1) longitudinal optical (LO) mode from doped samples. Two methods of theoretical fitting, one-mode (LO-plasma coupled (LOPC) mode) and two-mode (A(1)(LO) + LOPC) fitting, are employed to analyze this anomalous phenomenon. Theoretical simulations for temperature dependent Raman spectra by using two methods are critically examined. It turns out that one-mode method conforms well the experimental results, while two-mode method is untenable in physics. The non-monotonous variation of blue-red shifts with temperature for LOPC mode from doped 4H-SiC could be explained by the influence from ionization process of impurities on the process of Raman scattering. A quantitative description on temperature dependent Raman spectra for doped 4H-SiC is achieved, which matches well to experimental data.