Fig. 4

Crystal structure and lattice channel of K/P removal in KTP crystals. a K/P evaporation channels in a-axis KTP (view along a-axis). b Framework of TiO₂ by removing the K and P from the KTP (view along a-axis). c Crystal structure of anatase TiO₂ (view along 101 axis). d Ball and stick model of the transformation of KTP to TiO₂ (view toward 101 plane)