Low alpha-ray emission stannous oxide and method of producing the same

A method of producing stannous oxide having a low a-ray emission amount, the method comprising:

• a step (a) of dissolving tin containing lead as an impurity in a sulfuric acid aqueous solution, to prepare a tin sulfate aqueous solution and performing a first precipitation of lead sulfate in the tin sulfate aqueous solution;
• a step (b) of filtering the tin sulfate aqueous solution containing the lead sulfate obtained from the step (a) to remove the lead sulfate from the tin sulfate aqueous solution;
• a step (c) of performing a second precipitation of lead sulfate in the tin sulfate aqueous solution by adding a lead nitrate aqueous solution containing lead having an x-ray emission amount of 10 cph/cm2 or less to a first tank for over 30 minutes while stirring the tin sulfate aqueous solution, from which lead sulfate has already been removed, obtained from the step (b) at a rotation speed of at least 100 rpm to cause lead sulfate to be precipitated in the tin sulfate aqueous solution, simultaneously circulating the tin sulfate aqueous solution so that a circulation flow rate is at least 1 vol %/min with respect to a total liquid amount in the first tank while filtering the tin sulfate aqueous solution to remove lead sulfate which has been precipitated from the tin sulfate aqueous solution a second time;
• and
• a step (d) of adding a neutralizing agent to the tin sulfate aqueous solution obtained from the step (c) to collect stannous oxide.