Sr2IrO4 is an important material in the field of condensed matter physics, being a proposed J_eff=1/2 Mott insulator. Recent publications have shown that the reported low- and room-temperature space group (I4_1/acd) cannot be correct due to the presence of forbidden reflections over a wide temperature range. Small distortions can have dramatic effects on the electronic structure of iridate materials. The Ir-O orbital overlap is directly affected by IrO6 octahedral tilts and rotations. Therefore, the determination of the correct structure is essential for future theoretical and experimental investigations of this important system. The first objective of this experiment is to determine the correct space group for Sr2IrO4. The second is to investigate the (so far unexplored) high temperature phase transitions of this compound to understand the origin of the distortion at room temperature.