Synthesis of New (Pb,Ga)Sr 2 (Ca,Er)Cu 2 O z Superconductors under Ambient Pressure
H. K. Lee ∗
Department of Physics, Kangwon National University, Chuncheon 200-701, Korea (Received 29 July 2014 : revised 5 August 2014 : accepted 5 August 2014)
A search for superconductivity has been made for samples with compositions of (Pb
0.6Ga
0.4)Sr
2(Ca
1−yEr
y)Cu
2O
z(0.3 ≤ y ≤0.7) and (Pb
1−xGa
x)Sr
2(Ca
0.5Er
0.5)Cu
2O
z(0.2 ≤ x ≤ 0.75) synthesized by using a solid-state reaction method under ambient pressure. The X-ray diffrac- tion study shows that nearly phase-pure samples with a 1212 structure are obtained within a range of 0.3 ≤ x ≤ 0.4 and y = 0.5. The maximum superconducting transition among them achieved for the sample with x = 0.4 and y = 0.5, which exhibits an onset temperature of superconductivity, T
c, of about 23 K and a zero-resistivity temperature of 12 K. Thermoelectric power measurements indicate that the hole concentration of the sample can be varied by using both the Ga content in the (Pb,Ga) sites and the Er content in the (Ca,Er) sites.
PACS numbers: 74.72.-h, 74.72.Jt, 74.62.Bf, 74.25.Fy
Keywords: Synthesis, (Pb,Ga)Sr
2(Er,Ca)Cu
2O
z, New superconductor
:
0z ºÆ U Ø (Pb,Ga)Sr 2 (Ca,Er)Cu 2 O z ¾ ¹ Åy ¢= k8 ý V ê s° q ¶ ¥V R Ë
T
Ú£ Ó ∗
y
© " é ¶ @ / < Æ § Ó ü t o < Æõ , ð r ; 200-701
(2014¸ 7 Z 4 29{ 9 ~ Ã Î6 £ §, 2014¸ 8 Z 4 5{ 9 Ã º& ñ : r ~ Ã Î6 £ §, 2014¸ 8 Z 4 5{ 9 > F S X & ñ )
D
h Ðî r í ¸^ _ 0 p x$ í ` ¦ ¸ l 0 AK ¦ © ì ø Í6 £ xZ O Ü ¼ Ð (Pb
0.6Ga
0.4)Sr
2(Ca
1−yEr
y)Cu
2O
z(0.3 ≤ y ≤ 0.7) x 9 (Pb
1−xGa
x)Sr
2(Ca
0.5Er
0.5)Cu
2O
z(0.2 ≤ x ≤ 0.75) ¸$ í _ r ¼ # ` ¦ © · ú \ " f ½ + Ë
$ í
ô Ç Ê ê í ¸ : £ ¤$ í ` ¦ ¸ Ù þ ¡ . X- r] X ì r$ 3 z ´+ « > õ H © l ¸$ í \ " f 0.3 ≤ x ≤ 0.4 Õ ªo ¦ y = 0.5 { 9 M : _ é ß { 9 © _ 1212 © s + þ A$ í H d` ¦ Ð# Å Ò% 3 . þ j ¦ e > : r ¸ H x = 0.4 Õ ªo ¦ y = 0.5 { 9 M : ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, í ¸ s r : r ¸ x 9 q $ ½ Ós 0 s ÷ & H : r ¸ H y y 23 K, x 9 12 K
%
i . \ P l § 4 8 £ ¤& ñ õ Ð Â Ò' r ¼ # _ f . Ë 0 l x ¸ H (Pb,Ga) o _ Ga õ (Ca,Er) o _ Er_ u ¨ 8
|
¾ Ó` ¦ ¸] X # or ~ ´ Ã º e 6 £ §` ¦ · ú Ã º e % 3 .
PACS numbers: 74.72.-h, 74.72.Jf, 74.62.Bf, 74.25.Fy Keywords: ½ + Ë$ í , (Pb,Ga)Sr
2(Er,Ca)Cu
2O
z, D h Ðî r í ¸^
∗