Evolution of Metal-Trifluoroacetate Precursors in the Thermal Decomposition toward High-Performance YBa₂Cu₃O₇ Superconducting Films

Abstract

A thorough analytical study on the thermal decomposition evolution of the metal-trifluoroacetate precursor toward high-performance YBa2Cu3O7 superconducting films is presented. Evolved gas analysis (EGA), using Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS), as well as X-ray diffraction (XRD), was performed to determine the complete chemical decomposition reaction of the metal-trifluoroacetate precursors. It is noteworthy that, contrary to what had been previously described, HF was not detected in the released gas. Moreover, we present new processing conditions that successfully reduced and even eliminated the undesirable porosity of the pyrolyzed films. Focused-ion-beam (FIB) studies demonstrated that the formation of pores was related to a fast escape of the released gas during precursor decomposition. The oxygen partial pressure was determined to be a key parameter to control both the kinetics and thermodynamics of the decomposition reaction and, hence, the porosity. This is of great importance because dense films are required to achieve high critical current densities in YBa2Cu3O7 superconducting films.

Fabrication of YBCO Film Using a New Copper Precursor by Chemical Solution Method

“…The result is close to the decomposition behavior of all-TFA YBCO gel reported by Dawley et al [12] and Yoo et al [9]. This abrupt weight change is related to the amount of HF and COF 2 gas generation [4,16]. As result of this, the humid gas and the low heating rate were used to suppress the sublimation and to acquire the crackfree precursor films [3].…”

Thermal analysis of metal organic precursors for functional oxide preparation: Thin films versus powders

“…Although the usual aim of CSD is to obtain oxide films, sometimes decomposition of the precursor molecule leads to the formation of intermediate products such as metal carbonates or fluorides [2,34,18]. In fact, at present, the most promising precursors for YBCO production are fluorine-based [16,17].…”

Phase transition during sintering process before nucleation of TFA-MOD YBa2Cu3O7-δ films

“…The partial pressure of water, oxygen, the concentration of HF and temperature are main factors in the YBCO nucleation and growth. It has been suggested that reducing the fluorine content in the metal-organic precursors could help to lessen inhomogeneity in the resulting films [1,2] and the growth rate of the YBCO film is governed by Temperature, P H2O and P HF [3,4]. Takeshi Araki et al found that Y, Ba, and Cu trifluoroacetates decomposed to oxides or oxy-fluorides at 400°C in a humidified oxygen atmosphere, while Y and Ba trifluoroacetates which finally decompose to amorphous oxy-fluorides [5].…”