Laser processing as a tool for designing donor-substituted calcium manganite-based thermoelectrics

Abstract

In this work, the laser floating zone technique (LFZ) for donor-substituted calcium manganite-based thermoelectrics were assessed using Ca1-xPrxMnO3 (x = 0.03, 0.06, 0.1) as a model system. Fibres were grown by LFZ with pulling rates of 25, 100 and 200 mm h−1 in various atmospheres (air, vacuum and argon). Strongly non-equilibrium conditions imposed by LFZ promoted the formation of impurities in (Ca, Pr)MnO3 ceramic fibres, in several cases possessing dendritic structures. The results clearly indicate that careful optimization of the laser processing conditions is needed to produce the manganites with reasonable thermoelectric performance. Negative effects of the phase impurities, promoted by LFZ, on the transport properties can be minimized by additional heat treatment of the laser-processed fibres. The guidelines suggest that LFZ is a suitable technique for processing of thermoelectric perovskite-type manganites if optimized control over growth parameters and re-equilibration conditions is imposed.