The X-ray diffraction method was applied to measure the change of the lattice strain and domain switching in rhombohedral lead zirconate titanate (PZT) due to poling and applied strains. The lattice strain was determined from the linear relation between the diffraction angle and sin2ψ. The lattice strain measured by X-rays is at most 15% of the macrostrain determined from the dimensional change due to poling. A major part of the macrostrain was caused by domain switching. External loading induced domain switching and lattice strain. The lattice strain induced by external loading was at most 25% of the applied strain. The amount of domain switching was evaluated by the change of the intensity ratio of 222 diffraction to 222 diffraction. The intensity ratio for normal diffraction (ψ=0°) was decreased with the applied strain, because the spontaneous poling direction, 222 direction, turned to the loading direction. The broadening of X-ray diffraction profiles obtained from the diffraction plane perpendicular to the poling direction was the maximum, indicating the largest microstrain in the poling direction.
