Cubic Zirconia

Cubic Zirconia is made up of synthetic monocrystals of zirconium oxide (ZrO2) stabilized by doping rare-earth elements such as yttrium, erbium, cerium, neodymium, or cobalt, vanadium, chromium, iron, and others. First synthesized in 1972 by the “Laser Equipment Lab” of the Institute of Physics at the Russian Academy of Science, cubic zirconia has high optical properties, chemical resistance and hardness. It is an insulator that turns into a conductor under temperatures higher than 300 °С.

Colored cubic zirconia
Chemical formula    ZrO2
Hardness (Moh’s scale)    8
Density (g/cm³)          5,5 - 6
Refraction               2,15 – 2,18
Dispersion               0,059 – 0,065
Melting temperature, °С  2600 - 2750

There are two base crystalline variations of cubic zirconia: stabilized and partially stabilized (PSZ). They have different physical and chemical features.

Partially stabilized zirconia (PSZ)
PCZ crystals

High-purity cubic zirconia crystals are grown through oriented crystallization of melt in a cool container under high-frequency heating. Cubic zirconia technology was developed between 1970 and 1973 by V. Osiko, V. Alexandrov and other scientists from the Institute of Physics’ Laser Equipment Lab.

It includes the following stages:
  • batch mixing;
  • loading batch to container;
  • process of melting;
  • growing crystals through the oriented crystallization of melt;
  • extraction of crystals from crucible;
  • mechanical processing and sorting of crystals;
  • cleaning of crystalline waste for consequent melting and crystallization.
   The cool container creates the hard crust of initial zirconium oxide powder (lining, or garnissage) that surrounds the melted batch and becomes a substrate where cubic zirconia crystallizes. To make the melt conductive for high-frequency melting, some metallic zirconium is added to it under the low temperatures. Crystals grow as melt is cooling.

Cubic zirconia has many technical and jewelry applications. The technical applications of cubic zirconia are found in:
  • optics: the manufacture of high-temperature chemically inert radiation-resistant optical elements with high refraction indices and broad spectral bandwidths;
  • medicine, including ophthalmology: inert implants and safety scalpels; metal processing: cutting tools;
  • microelectronics: wafers for “conductor on insulator” structures; dyes for the cable industry, solid-state electrolytes for liquid and gas environment oxygen sensors.
  • RHT grows large – up to 5 kg – crystals of cubic zirconia for technical uses.
RHT is now the only Russian cubic zirconia manufacturer. Due to our exclusive cubic zirconia products (that are many shades including green, blue, deep blue, opalescent and that can also change color) we are able to remain global leaders in cubic zirconia manufacturing.