Preparation of nanostructured La0.7Ca0.3−xBaxMnO3 ceramics by a combined sol-gel and spark plasma sintering route and resulting magnetocaloric properties

This work proposes an original, easy to achieve and inexpensive route to synthesize manganite ceramics for magnetic refrigeration, combining sol-gel chemistry to Spark Plasma Sintering (SPS). The target La0.7Ca0.3−xBaxMnO3 (x=0, 0.1, 0.2) compounds are obtained as single phases which crystallize in the orthorhombic structure (Pnma space group). SPS allows a quick sintering at a relatively low temperature (700 °C in this work) compared to the conventional solid state method (≥1100 °C), leading to densified ultrafine grained pellets (85% of compactness). Magnetic studies show that Ba substitution does not affect significantly the relative cooling power (RCP) of these manganites, while it increases their Curie temperature (TC) by several tens of degrees. Typically, RCP values ranging between 267 and 270 J/kg (for a magnetic field change of 5 T) and TC between 205 and 245 K were measured when x was increased from 0 to 0.2, respectively. These results combined to the fact that the synthesis route is economically advantageous makes the obtained ceramics interesting as active refrigerants for magnetic refrigeration technology below room temperature.