Na-ion batteries might become a low-cost alternative to Li-ion batteries in the future. Suitable electrode materials, especially anode materials, are needed for Na-ion batteries. As possible candidates Cu0.5TiOPO4 and Fe0.5TiOPO4 were tested. While Cu0.5TiOPO4 does not react with Na+, Fe0.5TiOPO4 shows a specific charge of ≈600mAh/g upon the first sodiation and 280mAh/g in the first desodiation. In situ XRD in a new, versatile and reliable in situ cell revealed that Fe0.5TiOPO4 reacts via a conversion type reaction upon sodiation with an amorphisation of the sample.