Kang Du,Chang-Zhi Yin,Yan-Bo Guo,Xiao-Chuan Wang,Wen-Zhong Lu,Wen Lei
CaSn 1- x Ti x GeO 5 (0 ≤ x ≤ 1.0) ceramics were prepared using traditional solid-state reaction with sintering at 1275 °C – 1500 °C for 5 h. The Ti 4+ substitution for Sn 4+ inhibited the CaSnO 3 second phase of CaSnGeO 5 ceramic, and phase transition from triclinic with A 1 ¯ space group to monoclinic with A 2/ a space group and then to monoclinic with P 2 1 /a space group occurred in CaSn 1- x Ti x GeO 5 (0 ≤ x ≤ 1.0) ceramics. Evident changes in Sn/TiO 6 octahedron and Sn/TiO 6 octahedral chains were observed. A change in τ f from negative (‒62.9 ppm/°C) to positive (+18.7 ppm/°C) was achieved by controlling octahedral distortion. The large octahedral distortion contributed to near-zero τ ε for CaSn 1- x Ti x GeO 5 (0 ≤ x ≤ 0.8) ceramics. The broadening and shifting of ε r anomaly peaks for CaSn 1- x Ti x GeO 5 (0.8 ≤ x ≤ 1.0) ceramics greatly influenced τ ε , and the sudden increase in τ ε was attributed to the shift of ε r anomaly peaks to high temperature.
Canglong Li,Xuechi Lu,Xinshuai Niu,Boyuan Zou,Yao Zhao,Xuanjie Li,Yang Lu,Yongsong Luo
The magnetic refrigeration is achieved through the magnetocaloric effect of a magnetic system, which is considered a promising technology for achieving the required low temperatures in industry, daily life, and scientific research. This work experimentally investigates the magnetic behavior and magnetocaloric performance of Ho 2 CoMn 1- x Ti x O 6 (0 ≤ x ≤ 1) double perovskites. The experimental results reveal that a paramagnetic →ferromagnetic transition characterized by a sharp increase in magnetization is suppressed due to decoupling action of Ti 4+ with 3 d 0 spin configuration. As a result, the transition temperature T C reduces monotonically from 75 K at x = 0–37 K at x = 0.6, and no obvious ferromagnetic transition is identified at x = 0.8–1 due to the lack of Co 2+ –Mn 4+ interactions at so high Ti 4+ substitution concentration. In addition, the magnetocaloric effect is investigated by measuring the isothermal initial magnetization from 4 K to a temperature far above T C . The maximum magnetic entropy ( − Δ S M max ) under Δ H = 6 T does not exhibit significant variation from x = 0 (11.1 J kg −1 K −1 ) to 0.6 (11.5 J kg −1 K −1 ), while it increases noticeably from x = 0.8 (13.9 J kg −1 K −1 ) to 1 (17.2 J kg −1 K −1 ). The present work indicates that the cryogenic magnetocaloric effect can be improved by dilution effect of nonmagnetic ions.
危险品化学品经营许可证（带存储）