Impedance spectroscopy study on Ca~(2+) doped YCrO_3 ceramics

摘要

Polycrystalline YCrO_3 and Y_(0.8)Ca_(0.2)CrO_3 ceramic samples are studied subsequently using powder X-ray diffraction, Raman spectroscopy, X-ray photon spectroscopy and impedance spectroscopy to understand the effect of Ca doping on structural and electrical properties. Both samples have been prepared by conventional solid state reaction method. All the samples crystallize in Pnma orthorhombic structure without formation of any secondary phases confirming their phase-pure nature. Rietveld refinement of the X-ray data suggestes a decrease in unit cell volume. In Raman study, phonon modes shift to lower wave numbers and intensity leads to decrease due to doping at Y-site. The changes in phonon modes can be connected to the decrease in binding energy as observed in XPS studies. Further, impedance spectroscopy studies showed that the dc conductivity increases as Ca doped in YCrO_3. The doping with Ca reduced the activation energy for conduction. Both samples indicate an anomaly across ～ 470 K, diffuse phase transition.