Wafers of Tb-doped GdAlO3/α-Al2O3 eutectic were fabricated by the micro-pulling-down method using an Ir crucible with a 25 × 25 mm2 die. A prototype X-ray phase imaging detector was developed using a CMOS sensor with a fiber optic plate and the eutectic wafer. X-ray spots with an 8.24 μm period were observed using the detector. X-ray phase imaging of a nylon ball with a diameter of 4 mm was also carried out. It was observed that a phase change of approximately 2 μm occurs at the air-nylon interface. This technique of X-ray phase imaging can be realized in the absence of an absorption grating.