[Physics] Why doesn’t the coefficient of linear expansion decrease with increase in temperature

Question

If temperature is increased, then the change in temperature also increases. If the change in temperature increases, the coefficient of linear expansion should also increase according to the formula
(change in length/length*change in temperature)
But why isn't it so?

Answer 1

You want to say that since $$\alpha = \frac{\Delta l}{l_0 \Delta T},$$ then with change in temperature, the constant $\alpha$ should also change.

However, for small changes in temperature, the ratio $\frac {\Delta l}{\Delta T}$ remains fairly constant, such that $\alpha$ remains constant.