2) The rate of diffusion

Two ways to increase the rate of diffusion are to

(i) Increase temperature

(ii) Introduce defects by starting with reagents that decompose prior to or during reaction, such as carbonates or nitrates.

3) The rate of nucleation of the product phase

We can maximize the rate of nucleation by using reactants with crystal structures similar to that of the product ( topotactic and epitactic reactions).