PKN-a strong piezoelectric crystal
Dielectric, piezoelectric and electromechanical coupling properties of lead potassium niobate Pb/sub 2/KNb/sub 5/O/sub 15/ (PKN) crystals are reviewed in this paper. PKN has very strong coupling coefficients for bulk wave and surface acoustic wave, k 0.6-0.7 and k/sup 2/>10% in comparison with several piezoelectric crystals such as LN, LT, /spl alpha/-SiO/sub 2/, LBO, LGS, LiIO/sub 3/ and BNN. Transparent, brownish twin-free PKN crystals of 1" diameter by 2" length have been grown by the modified Bridgman method by us for the first time under a furnace temperature 1380-1400/spl deg/C and growth rate <0.5 mm/hr, so that research into the application of PKN crystals has become possible.