Complex oxides represent a class of materials with a plethora of fascinating properties like ferroelectricity, superconductivity, colossal magneto-resistance effect etc. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by the lattice effects opens a scientifically rewarding playground for both fundamental and application-oriented research. One such class of oxide materials is the perovskite manganites which exhibit large magneto-resistance effect commonly known as colossal magneto-resistance (CMR). In the present work we have studied the substitution effect on various physical properties like electrical resistivity, magneto-transport, AC susceptibility, DC magnetization, thermoelectric power and specific heat of such polycrystalline manganite materials. Manganite materials like Pr0.67Ba0.33MnO3 with large ionic size difference at the rare-earth site have been synthesized and their properties have been compared with the manganites having low ionic size mismatch effect viz. La0.67Ca0.33MnO3 and Pr0.67Sr0.33MnO3.