Optical and electrical properties of undoped ZnO films were investigated in this study. We find that the conductivity increased with increasing the ratio of (blue $\text{luminescence}+\text{green}$ luminescence) to ultraviolet luminescence [i.e., $(\mathrm{BL}+\mathrm{GL})∕\mathrm{UVL}$ ] defect emission intensities, due to the increase of the singly ionized oxygen vacancy. We deduce that the BL and GL are related to the oxygen-vacancy deep level and the yellow luminescence is attributed to the band-acceptor transition. We also find that poorer crystal quality may lead to the reduction of the optical transmittance. This suggests that these defects and the crystal quality interact to change the conductivity and optical transmittance of ZnO. The spectroscopic correlations may be used as a predictive tool to identify the quality of ZnO.

High ZT values of nanostructured Bi_2−xSb_xTe₃ for energy conversion are fabricated by hydrothermal methods followed by cold-pressing and sintering in an evacuated and encapsulated ampoule. We show that the sample with a nominal composition of x = 1.55 exhibits a dimensionless figure of merit ZT = 1.65 at 290 K and 1.75 at 270 K with significant 60–70% improvement of that of the commercial state-of-the-art Bi₂Te₃ materials around room temperature. The significant ZT improvement arises from the much-reduced thermal conductivity. The low thermal conductivity is mainly due to the increased phonon scattering in the nanostructured materials.

The authors report measurements of the electrical resistivity, Seebeck coefficient, and thermal conductivity for a series of misfit-layered oxides ${\mathrm{Ca}}_3{\mathrm{Co}}_{4-x}{\mathrm{Fe}}_x{\mathrm{O}}_{9+\delta }$ ($x=0$ , 0.05, 0.1, 0.15, 0.2) prepared by solid state reaction. Structural parameters are refined with superspace group of $X2∕m\left(0\mathrm{b}0\right)s0$ using powder x-ray diffraction data. With partial substitution of ${\mathrm{Fe}}^{+2}$ for ${\mathrm{Co}}^{+3}$ , the resistivity decreases, while the thermopower increases simultaneously. The $x=0.05$ sample exhibits a higher figure of merit $(Z=3.01\times {10}^{-4}{\mathrm{K}}^{-1})$ than that of ${\mathrm{Ca}}_3{\mathrm{Co}}_4{\mathrm{O}}_{9+\delta }$ $(0.33\times {10}^{-4}{\mathrm{K}}^{-1})$ at $300\mathrm{K}$ , indicating much improvement of thermoelectric characteristics via partial substitution of Fe for Co.