  We obtained amorphous-FeAs-free SmFeAsO1-xFx using a low temperature
sintering with slow cooling. SmFeAsO1-xFx is sintered at 980 {\deg}C for 40
hours and cooled slowly down to 600 {\deg}C. The low temperature sintering
suppresses the formation of amorphous FeAs, and the slow cooling introduces
much fluorine into SmFeAsO1-xFx. The superconductivity of this sample appears
at 57.8 K and the superconducting volume fraction reaches 96 %. To study the
change of fluorine concentration during the cooling process, samples are
quenched by water at 950 {\deg}C, 900 {\deg}C, 850 {\deg}C, 800 {\deg}C, 750
{\deg}C and 700 {\deg}C. It is found that fluorine is substituted not only at
the maximum heating temperature but also during the cooling process. The low
temperature sintering with slow cooling is very effective to obtain a
homogeneous SmFeAsO1-xFx with high fluorine concentration.
