Synthesis, superconductivity and ESR characterization of Rb3C60 crystals

Abstract

A one-step doping process of C~o crystals with three equivalents of rubidium to produce Rb3C~o crystals was developed. The Tc's for all Rb3C6o crystalline samples ( ~ 30.5 K) were higher than those of the powder samples (28 to 29.6 K), but consistent with the reported four-probe resistivity result for a doped C6o crystal (transition midpoint = 30.2 K). High superconducting shielding fractions (between 60 and 90%) and sharp magnetic transition widths (ATlo-9o between ~ 3 K and 0.7 K) were observed for the samples doped with Rb at temperatures of 300 to 450°C. The doping process, as well as the composition, of these samples were studied with the use of an ESR spectrometer. Two major components, RbC~o and Rb3C~o, were quantitatively characterized. The superconducting shielding fractions of these samples were found to be linearly correlated with the Rb3C~o content obtained from ESR measurements. Higher-temperature doping ( > 400 °C) favored the formation of Rb3C~o at the expense of severe C~o crystal fragmentation. The optimal doping condition to produce Rb3C~o crystals was found to be around 300 ° C.

Spherical Agglomeration of Safinamide Mesylate: A Case Study of a Simultaneous Control of Crystalline Landscape and Micromeritic Properties

“…As reported in the patent of Schlueter and Pawlak et al article, SAFIM could crystallize as a hemihydrate. However, the behavior upon hydration and dehydration of SAFIM is less detailed.…”

“…To date, three crystalline phases of SAFIM have been reported: two enantiotropically related polymorphs with a solid–solid transition temperature of 20 °C ( A1 and A2 high- and low-temperature forms, respectively) and a hemihydrate ( H1 ). , As structural purity is of key importance for the pharmaceutical industry, the study aims at proving that SAFIM can be obtained as A1 solid form with desirable flowability properties after an agglomeration process.…”

Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

“…EPR spectroscopy is a useful method to study defect centers of superconductive materials. [32][33][34] The method uses unpaired electron spins as messengers, whose signal responses provide precise information on their direct local environment. Therefore, EPR spectroscopy is well suited to help understanding the role of defect centers since it provides a sensitive means to monitor different paramagnetic states of vacancies 35 or paramagnetic metal ions; 36 the method thus complements other experimental techniques such as Raman spectroscopy.…”