How to get better Silver iodide

How to get better Silver iodide? For many people this is a strange object, and here's the introduction to it:

Silver iodide as the bright yellow micro crystalline powder, odourless, which has two kinds of alpha and beta type, type of alpha for cubic crystal, 6.010 g/cm3 density, melting point 558 ℃, boiling point of 1506 ℃. Beta type for the six-party crystal, density 5.683 g/cm3, heated to 146 ℃ or to the type. Insoluble in dilute acid. Water, slightly soluble in ammonia water, easy to dissolve in potassium iodide, potassium cyanide, sodium thiosulfate and methylamine, no matter the solid or the liquid silver iodide, all have the characteristic, can feel from ultraviolet to about 480 mm wavelength of the light. The "silver nucleus", which is broken down into tiny particles by light, is gradually turned into green black. Heated with ammonia, it is converted to white due to the formation of silver iodide - ammonia complex crystals.