錯体重合法によるCa置換YBa_2Cu_3O_<7-d>の合成とラマン散乱 Raman Scattering of Ca-Substituted YBa_2Cu_3O_<7-d> Synthesized by Polymerized Complex Method
Two types of Ca-substituted Y123 phase, (A) Y<SUB>1-0.75x</SUB>Ba<SUB>2-0.25x</SUB>Ca<SUB>x</SUB>Cu<SUB>3</SUB>O<SUB>7-d</SUB> and (B) Y<SUB>1-x</SUB>Ca<SUB>x</SUB>Ba<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-d</SUB> have been prepared by a polymerized complex method X-ray powder diffraction and complex magnetic susceptibility measurements have shown that only type (A) is virtually of single phase without any impurities such as BaCuO<SUB>2</SUB> and Y<SUB>2</SUB>BaCuO<SUB>5</SUB>. The superconducting transition temperature T<SUB>c</SUB> decreases from 92.2K (x=0) to 83.2K (x=0.2) with increasing x in (A). Furthermore, we investigated the effect of Ca-substitution on phonon Raman spectra of type (A) by using a micro-Raman spectrometer. Ba and 0(4) phonons are significantly shifted towards lower frequencies by 3cm<SUP>-1</SUP> and 4cm<SUP>-1</SUP>, respectively, when x is increased from 0 to 0.2. A possible origin of the decrease in both T<SUB>c</SUB> and Ba-0(4) layers phonon energies are discussed in terms of both hole doping in the CuO<SUB>2</SUB> planes and internal pressure induced by the Ca-substitution.
粉体および粉末冶金 43(9), 1065-1069, 1996-09-15
Japan Society of Powder and Powder Metallurgy