Correlation Between Enhanced ${\rm T}_{\rm c}$, Orthorhombicity and the Volume of the Unit Cell in Argon Preheated $({\rm Y}_{1-{\rm x}}{\rm Sm}_{\rm x}){\rm SrBaCu}_{3}{\rm O}_{6+{\rm z}}$

We report here on the preparation, X-ray diffraction with Rietveld refinement, AC susceptibility measurements and effect of heat treatments in (Y
_1-x
Sm
_x
)SrBaCu
₃
O
_6+z
. Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For each x, the [AO] treatment increases the orthorhombicity epsiv = (
b
-
a
) / (
b
+
a
) (for 0 les
x
les 1),
T

_c
(for
x
ges 0.4) and the distance
d
[
Cu
(1) - (
Sr
/
Ba
)] (decrease
T

_c
) for
x
< 0.5 and decrease it (increase
T

_c
) for
x
> 0.5 . When x increase from 0 to 1, epsiv decreases with
T

_c
[
O
]. However,
T

_c
[
AO
] decreases with epsiv until x = 0.2 and after it increases by 6 K to 85 K for x = 1 [AO]. A remarkable correlations were observed between
Tc
(
x
) and the volume of the unit cell
V
(
x
) ; and between delta
T

_c
(
x
) =
T

_c
[
AO
] -
T

_c
[
O
] and deltaepsiv(
x
). A combination of several factors such as decrease in
d
[
Cu
(1) - (
Sr
/
Ba
)]; increase in cationic and chain oxygen ordering; the number
p

_sh
(
x
) of holes by Cu(2) - O
₂
superconducting plans and in-phase purity for the [AO] samples may account for the observed data.