Forsterite single crystal and method for the manufacture of the same

In the method of manufacturing forsterite single crystals containing tetravalent chromium as luminescent ions comprising the steps of

• 1) forming pressure-pulverized powder by compressing oxide materials consisting of magnesium oxide, silicon dioxide and a chromium material by a static pressure press,
• 2) sintering the thus formed compressed powder in the temperature range of from about 700.degree. to about 1890.degree. C. for at least 4 hours in an atmosphere selected from the group consisting of the atmosphere, an oxygen gas, a nitrogen or argon gas, whereby sintered powder is obtained,
• 3) throwing said sintered powder into an inert atmosphere containing about 0.01-2.0% of oxygen, and
• 4) lifting up while heating the powder to its melting point and rotating it together with seed crystals to be grown up to desired single crystals,
• the improvement wherein the chromium material is a member selected from the group consisting of chromium trioxide and mixtures thereof containing 30-100% by weight of chromium trioxide and 0-70% by weight of dichromium trioxide, adding said selected member to said oxide materials in step 1) and sintering said powder in a non-reducing atmosphere.

In the method for manufacturing forsterite single crystals containing tetravalent chromium as luminescent ions comprising the steps of

• 1) forming pressure-pulverized powder by compressing oxide materials consisting of magnesium oxide, silicon dioxide and a chromium material by a static pressure press,
• 2) sintering the thus formed compressed powder from step 1) at a temperature range of from about 700.degree. to about 1890.degree. C. for at least 4 hours in an atmosphere selected from the group consisting of the atmosphere or an oxygen gas to obtain sintered powder,
• 3) throwing said sintered powder into an inert atmosphere containing about 0.01-2.0% of oxygen, and
• 4) lifting up while heating the powder to its melting point and rotating it together with seed crystals to be grown up to desired single crystals,
• the improvement wherein the chromium material is a member selected from the group consisting of dichromium trioxide and mixtures of more than 70% by weight up to 100% of dichromium trioxide with 0 up to less than 30% by weight of chromium trioxide, firing said mixture together with other oxide materials in an oxidizing atmosphere to obtain a fired body.