An apparatus for providing a signal indicative of a property of an earth formation includes: a carrier conveyable through a borehole; a neutron source disposed on the carrier and configured to emit neutrons into the earth formation; a radiation detector disposed on the carrier and configured to detect radiation from the earth formation due to interaction of emitted neutrons with the earth formation and to provide the signal indicative of the property; and a neutron shield configured to shield the radiation detector from emitted neutrons that did not interact with the earth formation; wherein the radiation detector shield includes a glass ceramic material having a plurality of nano-crystallites, each nano-crystallite in the plurality having a periodic crystal structure with a diameter or dimension that is less than 1000 nm that includes Li and/or Boron and a rare-earth element that have positions in the periodic crystal structure of each nano-crystallite.