Preparation and Study of the Perovskite-type La_(1-x-y)Ca_xSr_yMnO_3 Ceramics

A series of nanocrystalline powder of La(1-x-y)CaxSry,MnO3 was prepared by sol-gel technique, then was pressed and annealed to form ceramic. The results of magnetic measurement show that the Curie temperature of all the samples varies from 250K to 330K, and the maximal absolute value of ( M/ T) varies from 1.353 to 3.392A·m2/kg·K. The differential scanning calorimetry (DSC) measurements indicate that the latent heat in phase transition changes from 0.852 to 2.381J/g and increases with the increase of the maximal absolute values of ( M/ T). In addition, the maxial absolute value of ( M/ T) of La0.8-xCa0.20SrxMnO3(x =0.05, 0.08, 0.10) is also larger. Their Curie temperatures are adjacent to room temperature and they can be used as magnetic refrigeration materials at about room temperature.