Production and characterization of (K Na)(Nb Cu)O₃ crystal fibers grown by micro-pulling-down method

Abstract

Cu-doped sodium potassium niobate single crystal fibers (KNN-Cu) were grown by the micro-pulling-down technique under different atmospheres, namely, argon, synthetic air and oxygen. The structural analysis revealed that all fibers were grown in the perovskite phase with no secondary phase. In comparison with the precursors powders, the results from EDX showed no significative chemical changes, suggesting that monocrystalline and stoichiometric KNN-Cu fibers were produced. The ferroelectric phase transitions characterized by thermal strain measurements corroborated this assumption. The dielectric results showed that the fibers produced under synthetic air presented the best results. Piezoresponse measurements revealed domains with typically orthorhombic symmetry morphology.

Keywords:

• Ferroelectrics
• sodium potassium niobate
• single crystals
• micro-pulling-down
• PFM

Acknowledgments

The authors thank Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), CNPq (Grant 163761/2017-5) and FINEP for financial support. The authors also thank Federal University of São Paulo for providing the core research facilities - NAPCEM.