Testing thermal stability of orthorhombic GdCuP2.16 structure

Thermal stability with respect to a structural transformation and the crystal structure of the orthorhombic gadolinium copper phosphide GdCuP2.16 was investigated using powder diffraction techniques. The structure was refined from the data collected at room temperature to yield Pmm2 space group, a=5.3284(1), b=5.3868(1) and c=9.7486(2) Å. The refinement results agree well with the single crystal results [J. Solid State Chem. 155 (2000) 259]. Although the phosphide preserves the orthorhombic crystal structure up to 700°C, the thermal expansion along the a axis becomes larger than those along b and c axes above 500°C, indicating that a structural transformation is likely to occur at higher temperatures.