CHARACTERISTICS OF THE HIGH-TC SUPERCONDUCTING BI-PB-SR-CA-CU OXIDES DERIVED FROM AN ETHYLENEDIAMINETETRAACETIC ACID PRECURSOR

The modified sol-gel method using ethylenediaminetetraacetic acid as a chelating agent to prepare high-T(c) superconducting Bi-Pb-Sr-Ca-Cu oxides is reported. Results revealed that the desirable Bi-based compounds can be acquired by such a process with a high percentage of the 110 K phase and a T(c)(zero) of 108 K. On the other hand, a new method is proposed to quantitatively evaluate the volume fraction of the 110 K phase in Bi-based superconducting materials, mainly composed of 85 and 110 K phases. That is a lever-rule type of relation, V = (Y - 29.07-degrees)/(28.81-degrees - 29.07-degrees), where V is the volume fraction of the 110 K phase and Y = 2-theta for the X-ray diffraction peak emerging at about 29-degrees with a CuK-alpha radiation source and 28.81-degrees less-than-or-equal-to Y less-than-or-equal-to 29.07-degrees. The volume fraction of the 2223 phase estimated in this way is more reliable than that estimated by measuring the area ratios of XRD peaks and it is expected to be even more reliable than those derived from conventional methods based on perfect diamagnetism.