u00b0 c under a weak reducing atmosphere like a mixed gas atmosphere of h 2 and n 2 the produced phosphor had a composition of 0 1gdf 3 0 9bafcl eu 0 01 and when excited by x rays emitted light 5 times as bright as the light emitted by cawo 4 an aqueous suspension was prepared first by adding laf 3 5 g and baf 2 16 5 g to water then bacl 2 26 5 g and euf 3 0 05 g were dissolved in the suspension followed by drying at 150 u00b0 c and subsequent step of firing for 1 hour at 800 u00b0 c under a reducing atmosphere the resultant phosphor had a composition of 0 1laf 3 0 9bafcl eu 0 001 and emitted light having a peak at 385 nm the brightness of the light under x ray excitation was 3 times as high as that of the light emitted by cawo 4 the same procedures as in example 3 were followed except that used was a mixture of laf 3 14 7 g baf 2 17 6 g bacl 2 26 5 g and euf 3 1 5 g the resultant phosphor had a composition of 0 3laf 3 0 7bafcl eu 0 03 and when excited by x rays emitted light 2 times as bright as the light emitted by cawo 4 a mixture of laf 3 19.