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Ceramic YAG sheets (LEFT), Czochralski grown YAG (RIGHT)

Ceramic YAG (often called YAC) is produced by heating YAG powder under pressure until the powder bonds into a solid form. This process can take a few hour, and the result is a polycrystalline "sheet" that is not chemically pure and can not be used in scientific applications. Czochralski grown YAG crystals are pulled from a melt over an extended period of time (the two crystals above each took 12 days to make). The result is a monocrystalline structure with extreme purity and uniformity that can be used in scientific applications. Sometimes when developing a new formula, YAC is created as proof of concept before growing the crystal using the czochralski method.

YAC is grown in an array of colors, some of which are not grown as czochralski crystals. There is an abundant supply of YAC produced for the jewelry trade. The sintering process limits the thickness of the YAC sheets. They typically range from 6 mm but can go up as high as 12/13 mm limiting the size of the gems cut from them.

The chemical impurities and the polycrystalline structure of YAC can make gems cut from the material appear "fuzzy." This gives the gems an inner glow that can be either a bonus or detracting effect depending on ones preferences. This effect is maximized outdoors, especially when the sun is illuminating the gem from the side. This effect can be drastically minimized if certain cutting pattern are used (see below). 

The most popular (by far!) color of YAC has a green/blue color caused by a YB dopant. Below we compare green/blue YAC (Often falsely advertised on the internet as "PARAIBA YAG" as it is neither a YAG or a  "Paraiba" blue color) to blue/green YAG.

From Left to Right

  1. This video shows how drastically the "fuzzy" appearance of ceramic yag can be minimized by using the correct cutting pattern. The gem on the right, cut correctly, appears less "fuzzy."

  2. The drastic difference between the green/blue color of YAC and the blue/green color of  YAG

  3. The YAG gem on the left does not have the "fuzzy" appearance of the YAC gem on the right.

  4. An example of a properly cut large YAC that minimizes the "fuzzy" appearance and shows off the material's unique vivid and vibrant color at its best!

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