Pressure dependence of negative thermal expansion in Zr2(WO4)(PO4)2

Negative thermal expansion materials can experience significant stresses when they are used in composites. Under ambient conditions Zr2(WO4)(PO4)2 displays anisotropic negative thermal expansion (NTE) ( α v = − 14.0 ( 10 ) × 1 0 − 6 K − 1 , α a = − 7.9 ( 5 ) × 1 0 − 6 K − 1 , α b = 2.5 ( 5 ) × 1 0 − 6 K − 1 , α c = − 8.7 ( 2 ) × 1 0 − 6 K − 1 at 0 GPa). The effect of hydrostatic pressure on its thermal expansion characteristics was investigated by neutron diffraction between 300 and 60 K at pressures up to 0.3 GPa. No phase transitions were observed in the pressure and temperature range examined. The material was found to have a bulk modulus, B0, of 61.3(8) GPa at ambient temperature, and unlike some other NTE materials, pressure had no detectable effect on thermal expansion ( α v = − 14.2 ( 8 ) × 1 0 − 6 K − 1 , α a = − 7.9 ( 3 ) × 1 0 − 6 K − 1 , α b = 2.9 ( 5 ) × 1 0 − 6 K − 1 , α c = − 9.2 ( 2 ) × 1 0 − 6 K − 1 at 0.3 GPa).