| 摘要 |
PROBLEM TO BE SOLVED: To a lead-free piezoelectric ceramic composition excellent in piezoelectric characteristics by including a tungsten bronze-type compound oxide comprising Na, Ba, Nb and a specific content of Bi as metal elements. SOLUTION: This composition comprises a compound oxide containing Na, Ba, Nb and 3-6 wt.% (in terms of metal and based on the total weight of the composition) Bi as a principal ingredient. In the molar ratio composition formula xNaNbO3-yBaNb2O6-zBiNb3O9 [wherein, (x)+(y)+(z)=1], the composition preferably exists in the region surrounded by a quadrangle having apexes located at the points A (0.382, 0.560, 0.058), B (0.422, 0.520, 0.058), C (0.422, 0.505, 0.073) and D(0.382, 0.545, 0.073). The composition has a crystalline structure where almost all Bi are dissolved in crystal grains of ceramics to form a solid solution, and has the high Curie temperature of >=250 deg.C and low resonance frequency change with temperature of <=50 ppm/ deg.C. No danger of the vaporization/diffusion into the air and elution of lead doesn't exist. |
