sintered ceramics having such high radiation shielding capability and so easy to machine that they can be used as a radiation shield for radiation detectors are disclosed . the ceramics show a radiation shielding capability more than 90 % and preferably have high light reflecting performance . they may comprises rare - earth oxides such as gadolinium oxide , oxide of at least one of vanadium , tantalum and niobium and alkali - earth oxide which is used for a sintering agent . they can be used as a radiation shield in place of a molybdenum or tungsten radiation shielding plate and also as a light reflecting film instead of titanium dioxide film in a radiation detector for radiation ct equipment .