Crystal Growth and Negative Thermal Expansion Properties of a YMoO Single Crystal

A bulk-size single crystal of YMoO with 20 × 11 × 8 mm was successfully grown by the top-seed solution growth (TSSG) method. The full-width at half maximum of (100) and (010) crystal faces is 37 and 27 arcsec, respectively. The thermal conductivity coefficients , , , and are determined to be 1.519, 2.097, 0.445, and 0.997 W m K, respectively. It is worth noting that the YMoO crystal shows significant anisotropy thermal expansion properties, which exhibits a negative thermal expansion along the -axis ( = -5.11 × 10 K). The crystal structure analysis shows that the shrinking of Mo-O bond lengths along the -axis with the increasing temperature would be the main origin of the negative thermal expansion properties for YMoO crystal, which does not comply with the current mechanism.