Effect of Nb doping at Mn site on thermal expansion of Pr _0.7Sr_0.3MnO₃

In this study we present results on effect of Nb doping on thermal expansion of Pr_0.7Sr_0.3MnO₃. Thermal expansion measurements were done using three terminal capacitance method. The pure sample shows a jump at the insulator-metal (I-M) transition temperature, and with Nb doping, a fourfold decrease in the jump is found. Since thermal expansion is a bulk property, this suggests that the dopants are not in the form of local clusters; rather they are distributed uniformly throughout the sample. Temperature variation of Gruniesen ratio α/C_P shows that for temperatures below I-M transition, the ratio is weakly dependent on temperature. Pressure dependence on the transition temperature, dT_P/dP and jump in compressibility, Δβ, of these samples has been estimated using well-known Ehrenfest equations. The present results are in fairly good agreement with those reported in the literature.