This invention relates to rare earth tantalate and/or niobate phosphors which emit light under X-ray excitation, and an X-ray intensifing screen which utilizes these phosphors. The phosphor is represented by the general formula (I);...http://www.google.com.au/patents/US5120619?utm_source=gb-gplus-sharePatent US5120619 - X-ray phosphors and X-ray intensifying screen using the phosphor
