This document specifies test methods for the use of an integrating sphere to measure the optical properties of ceramic phosphor powders, which are used in white light-emitting diodes (LEDs) and emit visible light when excited by UV or blue light. This document specifies an absolute method to measure internal quantum efficiency and a substitution method to measure external quantum efficiency and absorptance. The substitution method uses reference materials whose external quantum efficiency and absorptance have been obtained in accordance with ISO 23946.