Control of Y₁Ba₂Cu₃O_x microstructures by polymer‐metal‐complex precursor synthesis

Abstract

SynopsisSingle phase Y,Ba,Cu,O, materials (1,2,3-compound) have been synthesized from polymermetal-complex (PMC) precursor between 860 and 950°C using a reaction time as short as 0.5 h. The morphology of the films and of fibers prepared by this process have been investigated. At low calcination temperatures the material is comprised of submicron grains, which are extensively interconnected forming a natural percolation network. Nodules with outgrowths are formed at intermediate temperatures; oblong shaped discs are obtained at high temperatures. The size and shape of grains are remarkably uniform in a given preparation; the former increases monotonically with the increase of calcination temperature. The 1,2,3-compounds produced are pure according to x-ray; they possess good superconducting properties (T, (midpoint) = 90.6 K; AT, (90%-10% resistivity) < 1 K) as prepared. Similar control of grain size and microstructure has been achieved for fibers of the 1,2,3-compound, the mechanical strength of which is inversely related to grain size. Pure Y,Ba,Cu,O, has also been prepare by the precursor method. X-ray diffraction gave unit cell dimension of a = 12.18 A, b = 5.66 A and c = 7.13 A belong to P,,,, or Pna2, space group. I. INTRODUCTIONThe discovery of a new class of ceramic oxide superconductors by Bednorz and Muller' and the observation that such materials exhibit superconducting transition temperatures above the liquid nitrogen temperature by Chu et. aL2 and many other scientists have generated intense research activities worldwide. These metal oxide superconductors (MOS) are usually prepared by traditional "ceramic" techniques? Particles of metal oxides and carbonates are ground into an intimate mixture and fired according to lengthy and exacting protocols. The initial product often contains undesired phases. For instance in the early preparation of YlBa2Cu30, (I) a mixture with a nominal composition of Y1,Ba,,Cu,~,O, was obtained which contained both I and the green Y2BaCu0, (11) phases in 1 to 2 r a t i~.~-~ Repeated grinding and firing can eliminate the undesired nonconductive phase. The powdery substance was finally compressed, sintered under oxygen, and slowly annealed to enhance intergrain contacts for good superconducting properties.The purity of the products of "ceramic" preparation is sensitive to a number of variables. Steinfink et. a1.6 had varied the composition (mole fraction) of the starting materials: 0.1 I YO,, I 0.45, 0.05 I BaO(BaC0,) 5 0.4, and 0.33 I CuO I 0.67, and found the products (reaction temperatures 920-1O0O0C for periods of 18-48 h) to be contaminated with Y2BaCu06,

Nanostructured Materials Preparation via Condensation Ways

“…Different types of polymers are used for preparing HTSC materials: PMAA [473][474][475], PAN [476,477], polyimides [478,479]. poly(N,N-dicarboxymethyl) allylamine [480,481], copolymers of acrylic acid [482,483] etc.…”

Hybrid polymer-inorganic nanocomposites

“…The polymer-analogous conversion method was used for the preparation of the Y 3+ , Ba 2+ and Cu 2+ complexes with polymethacrylic acid 251,252 and of the YBC chelates with polyamides 253,254 [gelatinisation with polyvinyl alcohol (PVA) can also be used]. 255 The superconducting ceramics based on these metallopolymers has T c = 80 ± 92 K, and the critical current density (J c ) is 150 ± 160 A cm 72 .…”