Photochromic　(PC)　luminescent　ferroelectric　materials　have　aroused　great　interest　because　of　their　potential　applications　in　non-contact　smart　information　storage　materials　and　devices.　In　this　study,　we　adopted　the　effect　of　rare-earth　ions　to　refine　the　grains,　combined　with　the　unequal　replacement　of　donor　doping　and　higher　temperature　sintering　methods　to　introduce　more　vacancy　defects,　to　simultaneously　improve　the　transmittance　and　photochromic　contrast　of　KNNLB-RE　ceramics.　The　optical　transmittance　of　a　typical　KNNLB-RE　＞　50%,　and　the　modulation　contrast　of　KNNLB-RE　is　relatively　significant,　such　as　ΔAbs　=　16.2%　and　ΔR　=　∼34%　for　KNNLB-Er.　More　interestingly,　the　Tc　of　KNNLB-RE　increased　by　about　10%-18%　(∼30　°C-50　°C)　due　to　the　degradation　of　the　relaxor-feature　and　the　increase　of　internal　stress,　which　broadens　the　temperature　application　range　of　KNNLB-RE　ferroelectric　ceramics.　In　contrast　to　most　opaque　inorganic　photochromic　materials,　the　KNNLB-RE　transparent　ceramics　can　express　multiple　pairs　of　＇off＇and　＇on＇codes　by　using　the　reversibly　decreased　and　increased　transmittance　and　PL　intensity;　thus,　these　materials　have　potential　in　the　applications　of　optical　sensors　and　memories　or　other　optical　data　storage　devices.　©　the　Partner　Organisations.