Investigations of KTiOPO4/SiO2 sol-gel materials

Sol-gel glasses with a composition close to KTiOPO, (films and bulk gels) are synthesised from titanium propoxide, din-butyl phosphate, potassium acetate, tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane. Thin films are drawn by dip coating. The annealing process consists of three steps: the evaporation of solvents, oxidation and removal of organics at 250 degrees C and 350 degrees C and the crystallisation between 500 degrees C and 800 degrees C. The structure formation is observed by FTIR spectroscopy (Fourier- Transform Infrared spectroscopy) and Karl-Fischer coulometry. UV- vis spectroscopic i(3+) investigations show, that the amount of T3+ ions increases with higher annealing temperatures and times. XRD measurements prove, that the crystallisation at least requires 600 degrees C At SiO2 containing bulk samples only KTiOPO, crystals are precipitated with an average diameter of about 50 mn. Annealing temperatures below 750 degrees C lead to a crystallisation of KTiOPO, crystals and higher temperatures to additional K4Ti2 57P2O16.9 crystals at SiO2 free samples. K4Ti4,P2O18.33 crystals are the only crystalline phase, found at gel film samples.