The effects of Ca substitution for Y on the electrical transport and thermoelectric properties of Y1−xCaxCoO3 (0⩽x⩽0.1), prepared by using the sol-gel process, were investigated in the temperature range from 300to780K. The results indicated that direct current electrical resistivity ρ of Y1−xCaxCoO3 decreased remarkably with increasing Ca content x as x⩽0.01, which could mainly be attributed to the increase of hole concentration due to substitution of Ca2+ for Y3+. The temperature dependences of the resistivity for Y1−xCaxCoO3 were all found to be basically consistent with small-polaron hopping conduction model. Although Seebeck coefficient S of Y1−xCaxCoO3 at low temperatures T<∼550K decreased remarkably with increasing x, it approached a limit value ∼150μV∕K at ∼800K for all the samples with different x, which was consistent well with the thermopower resulting from the degeneracy of electron configuration estimated from Heikes formula by assuming that Co3+ and Co4+ exist in low spin state. Experiments showed that thermal conductivity κ of Y1−xCaxCoO3 came mainly from its lattice component, whose decrease with increasing x could be chiefly ascribed to impurity-scattering effect due to Ca doping. The thermoelectric figure of merit ZT (=S2T∕ρκ) of Y1−xCaxCoO3 changed nonmonotonously with increasing doping content of Ca, and Y0.95Ca0.05CoO3 was found to have optimum thermoelectric properties with ZT=0.019 at 660K, which was about ten-fold greater than that of YCoO3, indicating that its thermoelectric properties could be improved effectively by appropriate substitution of Ca for Y in this compound.

Raman enhancement in a couple of nanocylinders (one made of silicon and one made of silver) has been calculated in our work. A formulation for enhanced Raman scattering of semiconductor cylinders is presented. The numerical calculation result based on the formulation indicates that the couple of nanocylinders (one made of silicon and one made of silver) can enhance the electric field in the silicon cylinder greatly and shows strong enhancement for volume average compared with bulk silicon. The largest enhancements per unit volume approach 107 times as compared with bulk crystalline silicon. The silicon and silver nanocylinder structures can combine useful features of the resonant excitations of silicon cylinder and the effect of resonant interaction between silicon cylinder and silver cylinder. This leads to the giant enhancement in the field inside the silicon cylinder and hence an increased Raman scattering. Moreover the results indicate that the interaction between the silicon cylinder and the silver cylinder is very strong under proper conditions.