| 摘要 |
PURPOSE:To obtain a lithium tantalate single crystal having a sonic velocity variation of surface acoustic waves of less than a specified value by controlling the direction shift of subgrains contained in a grown single crystal within a specified value. CONSTITUTION:This lithium tantalate single crystal is grown by using Li2O and Ta2O5 of high purities as raw materials by Czochralski process, etc. The grown crystal is converted to single domain and wafers are obtained from the crystal. Crystal qualities of the single crystal wafers are determined by X-ray diffraction and wafers having crystal direction shifts caused by subgrains in wafers, etc., of <=7 minute are selected. This method allows to obtain a lithium tantalate single crystal having a property of a sonic velocity variation of surface acoustic waves of <=+ or -0.01%. By using the obtained single crystal as a substrate, a tandem type electric pole is formed on its surface to obtain a surface acoustic wave element. The obtained surface acoustic wave element is used as a filter of a mobile communication telephone. |
