We report the fixing of photorefractive holographic gratings with high
efficiency in a sample of K1-yLiyTa1-xNbxO3 doped with Cu, V, and Ti.
Holograms are thermally fixed through the screening of a photorefract
ive space-charge field by a nonphotoactive species at elevated tempera
tures. Fixed holograms are revealed by illumination at lower temperatu
res. Diffraction efficiencies of 25% in a 0.54-cm-thick sample are mea
sured. Holograms undergo thermal decay with a 0.67-eV activation energ