The title compounds, sodium titanyl phosphate and potassium titanyl ph
osphate, are isostructural, belonging to a family of compounds with in
teresting non-linear optical properties. The effect of substitution of
K by Na has been analysed by X-ray diffraction at 110 K. The substitu
tion does not modify the geometry of the phosphate groups; however, th
e Ti-O coordination distances are changed, as well as the relative ori
entation of the Ti and P polyhedra.