Synchrotron X-ray powder diffraction under high pressures up to 33 MPa for mechanoresponsive materials

Equipment for synchrotron X-ray diffraction at high pressures up to 33 MPa with an accuracy of ±0.1 MPa using a liquid as a pressure-transmitting medium has been developed. This equipment enables atomic-scale observation of the structural change of mechanoresponsive materials under applied pressures. The validity of the equipment is demonstrated by observation of the pressure dependence of the lattice parameters of copper. The observed bulk modulus of copper was found to be 139 (13) GPa which is a good agreement with the literature value. The developed equipment was subsequently applied to a repeatable mechanoluminescence material, Li_0.12Na_0.88NbO₃:Pr³⁺. The bulk modulus and compressibility along the a and c axes were determined as 79 (9) GPa, 0.0048 (6) GPa^-1 and 0.0030 (9) GPa^-1, respectively, for the R3c phase. The advance of high-pressure X-ray diffraction will play an important role in understanding mechanoresponsive materials towards their atomic-scale design.