La(下標 0.67-x)Ca0.33MnO3系列樣品的磁熱效應

Polycrystalline samples of La(subscript 0.67-x)Ca0.33MnO3 (x=0.00, 0.02, 0.06, and 0.10) with different vacancies in La(superscript 3+)-site were prepared by sol-gel method. The grain sizes of samples were observed by SEM. XRD results show that the samples are single phase of perovskite-type oxides. The Curie temperatures and the magnetic entropy change of the samples were studied by VSM. The influence of the vacancy concentration in La(superscript +)site on their magnetocaloric properties has been investigated. The higher Curie temperatures close to room temperature and the larger magnetic entropy changes have been observed. The maximum magnetic entropy change, 2.78 J/(kg•K), is obtained near its Curie temperature (277 K) under the field of 1 T for La(subscript 0.67-x)Ca0.33MnO3 (x=0.02) sample.