Solvent extraction is the most widely used method for separation and purification of rare earth elements, and organic extractants such as di(2-ethylhexyl) phosphoric acid (P204) and di(1-methyl-heptyl) methyl phosphonate (P350) are most commonly used for industrial applications. However, the presence of impurity ions in the feed liquid during extraction can easily emulsify the extractant and affect the quality of rare earth products. Aluminum ion is the most common impurity ion in the feed liquid, and it is an important cause of emulsification of the extractant. In this study, the influence of aluminum ion was investigated on the extraction of light rare earth elements by the P204-P350 system in hydrochloric acid medium. The results show that Al3+competes with light rare earths in the extraction process, reducing the overall extraction rate. In addition, the Al3+stripping rate is low and there is continuous accumulation of Al3+in the organic phase during the stripping process, affecting the extraction efficiency and even causing emulsification. The slope method and infrared detection were utilized to explore the formation of an extraction compound of Al3+and the extractant P204-P350 that entered the organic phase as AlCl[(HA)2]2P350(o).Keywords:Al3+;light rare earths;P204;P350;impurity
Strong magnetic anisotropy in low-dimensional magnets leads to a significant rotating magnetocaloric effect, presenting new opportunities for the exploration of more efficient and streamlined refrigeration systems. In this study, we have successfully synthesized a series of centimeter-scale rare-earth-containing fluorocarbonates, K 4 RE 2 (CO 3 ) 3 F 4 ( RE = Ce, Pr, Nd, Sm, Eu, Tb, and Dy) through a supercritical hydrothermal method, featuring unique RE 2 O 12 F 4 magnetic dimers. The above materials' fundamental magnetism has been systematically investigated, and no long-range magnetic transitions were captured above 1.8 K. Based on the low-temperature specific heat results, the long-range magnetic ordering was found around 0.84 K and 0.97 K for K 4 Tb 2 (CO 3 ) 3 F 4 and K 4 Dy 2 (CO 3 ) 3 F 4 , respectively. Furthermore, the anisotropic magnetism of K 4 Tb 2 (CO 3 ) 3 F 4 and K 4 Dy 2 (CO 3 ) 3 F 4 reveals significant magneto-crystalline anisotropy, with the magnetic field ( B ) aligned along the RE 2 O 12 F 4 magnetic dimer, which acts as the easy magnetic axis. The maximum rotating field entropy change, − Δ S R max for K 4 Tb 2 (CO 3 ) 3 F 4 reaches approximately 9 J kg -1 K -1 around 17 K, while for K 4 Dy 2 (CO 3 ) 3 F 4 , it is approximately 5.5 J kg -1 K -1 near 11 K, both under a 7 T field applied along the c -axis. These findings highlight the potential of these compounds for magnetic refrigeration applications through a rotating crystallographic direction.
X-Ray or 254 nm UV-light charged storage phosphors have various promising applications such as in anti-counterfeiting and information storage. However, developing such storage phosphors with high charge carrier storage capacity remains challenging. In this work, photoluminescence spectroscopy, thermoluminescence (TL), and vacuum-referred binding energy (VRBE) diagram were combined to study the trapping and liberation processes of charge carriers in Bi3+ and/or Ln3+ (Ln = Tb, Pr, or Dy) doped LiLuGeO4. Unintended defects act as good electron trapping centers, while Bi3+, Tb3+, and Pr3+ act as hole-capturing and recombination centers. Dy3+ does not act as an electron trapping center but as a luminescence center by energy transfer from Bi3+ → Dy3+. The ratios of the integrated TL intensities between 303 K and 650 K for LiLuGeO4:0.005Bi3+, LiLuGeO4:0.005Bi3+,0.005Tb3+, or LiLuGeO4:0.005Bi3+,0.005Dy3+ after X-ray charging to that of the state-of-the-art BaFBr(I):Eu2+ is about 1.24, 0.59, and 0.90, respectively. More than 10 h or 40 h afterglow was measurable in both LiLuGeO4:0.005Bi3+ and LiLuGeO4:0.005Bi3+,0.005Tb3+ after X-ray or 254 nm UV-light charging. The stored charge carriers stored can be efficiently excited to produce optically stimulated luminescence with a wide range 365 nm UV-light to 850 nm infrared laser beam. Proof-of-concept colour-tailorable afterglow, X-ray irradiation time or sample mass-dependent dosimetry, and optically-stimulated luminescence with a wide range of 365 nm UV-light to 850 nm infrared laser stimulation will be demonstrated for anti-counterfeiting, information storage, and display applications in the developed Bi3+ and/or Ln3+-doped LiLuGeO4. This work not only reports Bi3+ and/or Ln3+ doped LiLuGeO4 storage phosphors with excellent charge carrier storage capacity but also deepens our understanding of the afterglow and storage phosphors and luminescence mechanisms, which can guide us to explore new afterglow and storage phosphors for multimode applications.
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