Effect of Mo substitution on the structural and transport properties of Bi2Sr2Ca2Cu3−xMoxO10+y system

The glass samples with nominal composition of Bi2Sr2Ca2Cu3−xMoxO10+y, where x = 0.5, 1.0, 1.5 and 2.0, were prepared using glass-ceramic method. The structural, thermal and transport properties of the samples prepared were investigated. After x = 1.0 substitution level glass formation was diminished and crystallized samples were obtained. XRD and SEM investigations showed that all the samples have multiphase and complex crystal structures. Crystallization activation energy, Ea, was calculated using both Augis–Bennett method and Kissinger method. Calculated Avrami parameter, n, suggested that diffusion-controlled growth mechanism exists for all samples. It was seen that Tc and T0 decreased as the Mo concentration is increased. The normal state resistance and hole concentration increases by increasing the Mo level. Negative thermoelectric power above Tc and positive thermoelectric power below T0 were found for all the substitution cases and heat treatment cycles indicating that both type of carriers (holes and electrons) are present for all the samples prepared. We analyzed the thermoelectric power as a function of temperature with “Two band model with linear T term” and “Xin's two band model”. Thermal conductivity κ(T) measurements were carried out between 300 and 30 K. The magnitude of κ was suppressed when Mo was increased in the BSCCO system. Results obtained give an evidence for increase of the quasi-particle mean free path.