Self-Propagating High-Temperature Synthesis of Chromium Substituted Lanthanide – Barium – Copper Oxides,
(Ln = Y; La; Nd; Sm and Yb)
Maxim V. Kuznetsov1, Ivan P. Parkin2, Yuri G. Morozov1 and Alexander G. Merzhanov1
1Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences,
Chernogolovka, Moscow Region, Russia
2Department of Chemistry, Christopher Ingold Laboratory, University College London, London, UK
A series of MBa2Cu3-xCrxO7-y (M = Y; La; Nd; Sm and Yb; x = 0, 0.05, 0.15, 0.25) materials were synthesized in air by self-propagating high-temperature synthesis (SHS) involving reaction of stoichiometric mixtures of rare-earth metal (III) oxide, barium peroxide, copper metal, chromium (III) oxide and sodium perchlorate. All the SHS processes were followed by sintering in oxygen at 950°C for 2h. The products were characterized by SEM, X-ray powder diffraction, UV, superconductive transition temperatures (Tc) and magnetic susceptibility (c) measurements. X-ray diffraction data showed that single phase orthorhombic (or tetragonal for M = Nd) materials were produced. All series of materials showed a systematic increase in lattice parameters and unit cell volume with chromium content (M = Y: x = 0, V = 174.25 Е3; x = 0.25, V = 175.10 Е3). Thermal stability of all the SHS prepared materials increased with x. Oxygen content of all the samples increased with x, but did not exceed 7.0. Superconductivity transition temperature decreased with chromium substitution in all systems (98-77 K). Magnetic susceptibility decreased with chromium substitution.