Single crystal growth and structure refinement of hollandite-type K1.98Fe1.98Sn6.02O16

•Single crystal of K1.98Fe1.98Sn6.02O16 was grown by the flux slow cooling method.•Optimum condition was 60 wt% {(K2O)1(Fe2O3)1(SnO2)1} and 40 wt% {(K2O)2(MoO3)1(B2O3)1}.•Needle like single crystal had 120 μm width and 3 mm length at a maximum.•Final R and wR values showed 2.24% and 6.23% respectively in the structure refinement.

Single crystals KxFexSn8−xO16 (KFSO, x~1.98) were grown by the flux slow cooling method. Needle like single crystal having 120 μm width and 3 mm length at a maximum was obtained by slow cooling to 1000 °C at a rate of 2 °C h−1 using starting materials with a 40 mol% crystal composition of (K2O)1(Fe2O3)1(SnO2)1 and a 60% flux composition of (K2O)2(MoO3)1(B2O3)1. KFSO single crystal was refined and calculated atomic coordination, bond length and so on from the x-ray diffraction method. Final R and wR values showed 2.24% and 6.23%, respectively.