Zirconia nanocrystals are the best materials to combine with various resins into a
transparent high-index composite. Such composite is crucial for the manipulation or enhancement
of light in devices such as Organic-Light-Emitting-Diode (OLED) or Liquid-
Crystal-Displays (LCD) that surrounds us today. To make a transparent composite, the
nanocrystals have to be small (<10nm), un-agglomerated and fully dispersed in resins. They
must also be crystalline to provide a better refractive index. Furthermore, since the index of a composite is determined
by the volume fraction of the constituents, a substantial increase can only be achieved with a high
zirconia loading, usually more than 50wt%. Consequently, the price of zirconia nanocrystals should not be too
expensive compared to that of common resins. This requirement excludes many synthesis methods reported in
the scientific literatures that employ delicate chemicals or require elaborate procedures. On the other hand,
many simpler and large-scale processes for the production of dispersible zirconia nanocrystals have been patented
by different companies. A review of the latest development is presented in this paper. Focus is placed particularly
on the size, crystalline phase and the dispersibility of the products, as well as on their associated cost.
Keywords: Dispersion, hydrothermal, sovothermal, nano-composite, nanocrystal, refractive index, zirconia.
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