Evaluation method for thermal expansion properties of titania-containing silica glass body, and manufacturing method for titania-containing silica glass body

A method for evaluating thermal expansion properties of a titania-containing silica glass body, comprising:

• a measurement step of each non-destructively measuring, for the titania-containing silica glass body, a physical parameter that fluctuates depending on a titania concentration and a physical parameter that fluctuates depending on a fictive temperature, at a predetermined temperature Tx, to obtain measured values of a plurality of physical parameters;
• a calculation step of calculating a coefficient of thermal expansion of the titania-containing silica glass body and a slope of the coefficient of thermal expansion of the titania-containing silica glass based on the measured values of the plurality of physical parameters obtained, respectively by using a linear relational expression expressed by the plurality of physical parameters;
• and
• an evaluation step of evaluating the thermal expansion properties of the titania-containing silica glass body based on the calculated coefficient of thermal expansion and slope of the coefficient of thermal expansion.