Growth and Characterization of KNbO₃ Single Crystal by Vertical Bridgman Method

Single crystals of potassium niobate (KNbO₃) were grown by the vertical Bridgman method. The crystal was cut into 3 × 3 × 0.7 mm³ plates, and dielectric constants and resonance characteristics were observed as a function of the magnitude of the electric field used in the poling treatment. With [001]_pc poled crystal, which stands for [001] direction in pseudocubic crystal lattice, no large change in properties resulted even if the electric field was changed. However, with [101]_pc poled crystal, a reduction in the dielectric constant, a shift to a higher resonance frequency, and an increase in the phase angle in the inductive reactance region were observed when the electric field became larger than approximately 70 V/mm. These results can be systematically explained by the relative directions of the dipole moment and the electric field, and the resulting movement.

Keywords:

• KNbO₃ single crystal
• vertical Bridgman method
• poling treatment
• piezoelectric property
• dipole moment

Acknowledgments

Paper originally presented at AMF-4, Bangalore, India, December 12-15, 2003.