Monocrystalline zirconia without low-temperature degradation properties and method for growing same

Abstract

A method of growing a zirconia single crystal includes preparing a mixture of ZrO 2 and Y 2 O 3 for growing the zirconia single crystal, charging the raw material and a melting seed in a skull crucible for growing the zirconia single crystal using a high-frequency induction heating device, supplying power to the high-frequency induction heating device to melt the raw material, maintaining an output power of the high-frequency induction heating device to soak the melted raw material, first-elevating an induction coil of the high-frequency induction heating device to produce a seed, second-elevating the induction coil of the high-frequency induction heating device to grow a single crystal, cutting off power to the high-frequency induction heating device when completing growth of the zirconia single crystal, and cooling the zirconia single crystal. The method has excellent physical properties free from low-temperature degradation and thus enables precise machining.

What is claimed is: 
     
         1 . A method of growing a zirconia single crystal, the method comprising:
 preparing a mixture of ZrO 2  and Y 2 O 3  as a raw material for growing the zirconia single crystal;   charging the raw material and a melting seed in a skull crucible for growing the zirconia single crystal using a high-frequency induction heating device;   supplying power to the high-frequency induction heating device to melt the raw material charged in the skull crucible;   maintaining an output power of the high-frequency induction heating device to soak the melted raw material;   first elevating an induction coil of the high-frequency induction heating device at a first elevation rate, thus producing a seed;   second elevating the induction coil of the high-frequency induction heating device at a second elevation rate, thus growing a single crystal; and   cutting off power to the high-frequency induction heating device when completing growth of the zirconia single crystal in the skull crucible, and cooling the zirconia single crystal grown in the skull crucible while allowing the zirconia single crystal to stand in the skull crucible.   
     
     
         2 . The method of  claim 1 , wherein the raw material comprises ZrO 2  and Y 2 O 3  at a composition ratio ranging from 95:5 wt % to 93:7 wt %. 
     
     
         3 . The method of  claim 1 , wherein the preparation of the mixture comprises selecting a raw material seed having a size of 10 to 30 μm from the raw material, and the charging of the raw material comprises charging the raw material seed and then the raw material. 
     
     
         4 . The method of  claim 3 , wherein the raw material seed is charged to a height of 5 to 40 mm from a bottom of the skull crucible. 
     
     
         5 . The method of  claim 1 , wherein the supply of the power comprises gradually increasing the output power of the high-frequency induction heating device to a melting output power for an initial 10 min and then maintaining the melting output power for 50 min. 
     
     
         6 . The method of  claim 5 , wherein a magnitude of the output power of the high-frequency induction heating device in maintaining the output power is identical to a magnitude of the power to melt the raw material charged in the skull crucible. 
     
     
         7 . The method of  claim 1 , wherein the maintaining of the output power is performed for at least 5 hr. 
     
     
         8 . The method of  claim 1 , wherein the first elevation rate is 2 mm/hr or less. 
     
     
         9 . The method of  claim 1 , wherein the second elevation rate is 1 to 20 mm/hr. 
     
     
         10 . The method of  claim 1 , wherein the supply of the power is performed under the condition that the induction coil of the high-frequency induction heating device is elevated by a predetermined height from a bottom of the skull crucible. 
     
     
         11 . The method of  claim 1 , wherein the skull crucible has a diameter of 20 to 50 cm. 
     
     
         12 . The method of  claim 1 , wherein in the second elevation, the grown zirconia single crystal is cooled at a cooling rate of 70 to 110° C./hr.