The physical and electromechanical requirements for relaxor-based piezoelectric single crystals of lead magnesium niobate–lead titanate (PMN-PT) and lead zinc niobate–lead titanate (PZN-PT) solid solutions of perovskite structure, with poling along the crystallographic c-axis (i.e., the [001]-direction), that are intended for fabrication into single plates, multilayer plate devices, and composites with other passive materials for use in medical, industrial, and military transducers, actuators, and sensors are covered in this standard. Definitions of terms and recommended practices for measuring the physical and electromechanical properties of these materials are also included in this standard.