Thermal expansion and spin gap in the normal state of YBa2Cu3Oy with La doping and oxygen-deficiency

We have synthesized the La doped YBa2−xLaxCu3Oy ceramic cuprates with <f>x&les;0.30</f> by the solid state reaction technique under the quenching temperature from 350 to 650 °C. X-ray diffraction and scanning electron microscopy studies indicate that all the synthesized samples contain one single phase. La is replacing for Ba at Ba-site in YBa2Cu3Oy. The unit cell volume varies with La content and with the quenching temperature. The thermal expansion for the unit cell volume at different quenching temperature is discussed. For the full oxidation samples the zero resistance temperature, <f>Tc0</f>, is almost unchanged with <f>x&les;0.20</f> whilst <f>Tc0</f> decreases with the increase of La content for the quenched samples. The spin gap opening temperature, <f>Ts</f>, for all the quenched and annealing samples are determined from the temperature dependence of resistance. [Copyright &y& Elsevier]