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.
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