Structural, dielectric, and electrical properties of cerium-modified strontium manganite ceramics

A solid-state reaction technique was used to make cerium (Ce) modified strontium manganite SrMn0.9Ce0.1O3 (SMCO). The Goldschmidt's tolerance factor of 0.95 and the Sure Independence Screening and Sparsifying Operator (SISCO) tolerance factor of 4.02, both are within the permissible range. SMCO's average crystallite size and micro-lattice strain were determined to be 59.6 nm and 0.439%, respectively. Analysis of the micrograph captured by the scanning electron microscopy (SEM) technique revealed the average grain size of 19.2 mu m of the SMCO. The optical bandgap of the SMCO was found to be 4.53 eV for direct allowed transition for photovoltaic applications. The existence of + 4 oxidation state of both Ce and Mn in the SMCO has been ascertained by the X-ray photoelectron spectroscopic technique. The bulk resistance (R-b) decreases from 1.02 x 10(5) to 1.09 x 10(3) omega on increasing the temperature supports the negative temperature coefficient of resistance (NTCR). The semiconductor nature of the material is further validated by the semicircular pattern of Nyquist and/or Cole-Cole plots. The observed change in activation energy with temperature proposes that the conductivity (sigma(ac)) behavior of the material is due to the thermal activation phenomenon. The evaluation of the field-dependent polarization (P-E) hysteresis loop was also carried out to obtain the coercivity, remnant polarization, maximum electric field, and maximum (saturation) polarization which support the possibility of ferroelectricity in the material. The leakage-current plots between (log J versus log E) at selected temperatures support the existence of Ohmic conduction in the material at low voltages.