Crystal growth of ZrW ₂O ₈ and its optical and mechanical characterization

ZrW ₂O ₈ is known for its isotropic negative thermal expansion over a wide of range of temperature from -272 to 777 °C. However, ZrW ₂O ₈ melts incongruently at 1257 °C and is stable only over a short temperature interval between 1105 and 1257 °C. This makes the growth of single crystals a formidable challenge. In order to study the intrinsic properties of this compound, a repeatable, viable single crystal growth strategy is required. Here we report a simple, self-seeding, self-fluxing single crystal growth process which resulted in single crystals of ZrW ₂O ₈ up to about 4 mm in size. Grown crystals were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Mechanical properties of the crystals were studied using nanoindentation.