Synthesis,Phase Transition of La0.69Sr0.31MnO3 Nanoperovskites Toward Its Versatile Structural,Electrical and Mechanical Properties Employing Ultrasonic Measurements

The present investigation correlates the propagation of ultrasonic waves with various micro structural features of nano La_0.69Sr_0.31MnO₃ (LSMO) perovskites with different grain sizes. A solid state reaction followed by the ball milling technique was used to synthesize the nano LSMO perovskite samples with various grain sizes. The occurrence of ferro-paramagnetic transition temperature (T_c) was explored through the observed anomalous behaviour in ultrasonic velocities, attenuations and elastic moduli. As the particle size gets reduced, lower T_c and broader transitions are observed due to the distribution of grain boundaries. The diffusion of the FM–PM phase transition along with decrease in T_c is correlated due to the effect of particle size. Furthermore structural, vibrational and electrical properties of nanosized LSMO perovskite samples with different grain sizes were studied by XRD, FTIR, BET surface area measurement, HRSEM, TEM and four probe conductivity studies. The phase of the synthesized nano LSMO perovskite samples are perfectly indexed to pure rhombohedral perovskite type crystal structure. The conductivity study proves the semiconductor nature of the nano LSMO perovskite samples. In addition to this, the peak broadening in ultrasonic studies at phase transition is in line with the observation made from the XRD pattern for the prepared nano LSMO perovskite samples.