[en] Full text: Phosphate materials are of great interest to materials science. Metal phosphate compounds are known to exhibit conductive properties for battery use [1], photocatalytic abilities to decompose other compounds [2], the ability to conduct protons [3], etc. High temperature sintering techniques were used to produce the diphosphate series K₂Cu_1-xFe_xP₂O₇. The material forms two different modifications, a tetragonal (P-42₁m) and an orthorhombic modification (Pbnm) as shown in Figure 1. The crystal structure was determined through the use of powder X-ray diffraction (PXRD). PXRD patterns show a shift in peaks to lower angles with increasing iron content, which is consistent with an increase of lattice constant parameters. The presence of additional phases such as KPO₃ can also be observed. UV-Vis measurements show how the transitions change which increasing amounts of iron and different modifications. Tauc plots revealed that the material has a direct band gap of approximately 3 eV. IR measurements revealed that water had been absorbed by the material and there a slight shift in peak position with increasing iron content. First magnetic measurements did not show any long-range ordering down to 2 K, the compounds remained paramagnetic. The K₂CuP₂O₇ and K₂Cu_0.75Fe_0.25P₂O₇ samples show short-range antiferromagnetic contribution across both modifications. (author)