Influence of hole filling by La and hole doping by Ca on the superconductivity of

Abstract

The structural and superconducting properties of ( samples have been studied by x-ray diffraction, resistivity, a.c. susceptibility and oxygen content measurements. The effect of increasing La concentration in is in lowering the carrier concentration and decreasing , which is attributed to hole filling by La. This suppression of has been compensated by appropriate hole doping with Ca in (, which shows that for a fixed La content increases dramatically as the Ca content increases. For instance, in the oxide (, the increases from 35 K (x = 0.0) to 82 K (x = 0.4, compensated oxide) as the hole filling by La is completely balanced by hole doping form Ca.

Contrasting Effects of Ca[sup 2+] and Ho[sup 3+] Substitutions on Superconductivity and Excess conductivity of (Ho[sub 1−x]Ca[sub x])(Ba[sub 2−y]Ho[sub y])Cu[sub 3]O[sub 7−δ]

“…On the other hand, Ca 2+ substitution at RE 3+ site causes recovery of T c in underdoped RE123 samples [1,2]. Similar works have also been reported for other RE123 systems [3][4][5][6][7]. Similar works have also been reported for other RE123 systems [3][4][5][6][7].…”

“…Substitutions of trivalent RE 3+ at the Ba site have been reported to lower critical temperature, T c with increasing RE 3+ concentration [1,2]. Interestingly, a combination of both Ca 2+ substitution at Nd 3+ site and La 3+ at Ba 2+ site showed hole filling by La 3+ was completely balanced by hole doping due to the Ca 2+ substitution [1,3]. Interestingly, a combination of both Ca 2+ substitution at Nd 3+ site and La 3+ at Ba 2+ site showed hole filling by La 3+ was completely balanced by hole doping due to the Ca 2+ substitution [1,3].…”

Influence of hole filling and pair breaking by Nd and hole doping by Ca on the superconductivity of NdBa2Cu3Oz

“…Four Nd-doped samples (y = 0.1 to 0.4) displayed nearly tetragonal structure, whereas all the five Ca-Nd doped samples (x = 0.1, 0.2, 0.3 and y = 0.3; x = 0.2, 0.4 and y = 0.4) remain orthorhombic with distortion (b − a)/(b + a) very close to that of pure NdBCO. The refined unit cell parameters for Er(Ba 2−y La y )Cu 3 O z are reported elsewhere [19], exhibiting orthorhombic structure for y = 0.0 to 0.3 and tetragonal structure for y = 0.4. It is interesting to note that the Nd-doped NdBCO samples undergo suddenly an orthorhombic to tetragonal transition at y > 0.1 whereas the La-doped ErBCO [19] and YBCO [10,13] samples display the same orthorhombic to tetragonal transition at y = 0.4.…”

“…The refined unit cell parameters for Er(Ba 2−y La y )Cu 3 O z are reported elsewhere [19], exhibiting orthorhombic structure for y = 0.0 to 0.3 and tetragonal structure for y = 0.4. It is interesting to note that the Nd-doped NdBCO samples undergo suddenly an orthorhombic to tetragonal transition at y > 0.1 whereas the La-doped ErBCO [19] and YBCO [10,13] samples display the same orthorhombic to tetragonal transition at y = 0.4. This indicates that the magnetic character of Nd suppresses orthorhombic structure much faster than the non-magnetic La substitution for Ba in RBCO.…”

Effect of Doping of Zn and Ca into ErBa2Cu3O7−δ Superconductor Prepared via Co-precipitation Method

“…Essentially, by varying the type and amount of dopant, different properties could be expected, which offers exciting possibilities to prepare material with desired properties. Several re- ports showed that doping causes a prominent effect towards structural, electrical, and magnetic properties of the superconductor [6,7], and [8]. Researchers found that valence of dopant plays an important role in determining the effective copper valence where the T c is influenced [9].…”