Effect of hydroxyl group on global and local structures of hydrothermally grown KNbO3 nanorods

Structural and Piezoelectric Properties of (Na1−xKx)NbO3 Platelets and Their Application for Piezoelectric Nanogenerator

“…Figure (a) shows the FT‐IR spectra of the NKN platelets synthesized at different temperatures for different times. The FT‐IR spectra of the NKN platelets synthesized at 500°C and 600°C for 6 h exhibited the broad peaks at around 3200 and 1643 cm −1 formed by the overlap of the O–H stretching vibrations of H 2 O and hydroxyl ions . These absorption peaks did not appear in the spectra of specimens synthesized at 600°C for 12 h, suggesting that the NKN platelets synthesized at 500°C and 600°C for 6 h contained a small amount of both OH − and water.…”

“…Therefore, the TGA results coincide with those derived from the FT‐IR spectra of the specimens. The weight loss occurring at temperatures above 600°C could be ascribed to the evaporation of alkaline ions . The OH − molecules are considered to exist in the O 2− sites, and metal vacancies could be formed in the matrix to maintain the charge neutrality of the material.…”

“…The FT-IR spectra of the NKN platelets synthesized at 500°C and 600°C for 6 h exhibited the broad peaks at around 3200 and 1643 cm À1 formed by the overlap of the O-H stretching vibrations of H 2 O and hydroxyl ions. 10,[26][27][28][29][30] These absorption peaks did not appear in the spectra of specimens synthesized at 600°C for 12 h, suggesting that the NKN platelets synthesized at 500°C and 600°C for 6 h contained a small amount of both OH À and water. The absorption band at 842 cm À1 could be attributed to [Nb 6 O 19 ] 8À , which can be observed in the KNNH precursor.…”

“…The weight loss occurring at temperatures above 600°C could be ascribed to the evaporation of alkaline ions. 10,[26][27][28] The OH À molecules are considered to exist in the O 2À sites, and metal vacancies could be formed in the matrix to maintain the charge neutrality of the material. Therefore, the presence of OH À molecules induced metal vacancies in the matrix.…”

Observation of three crystalline layers in hydrothermally grown BiFeO3 thick films

“…27 Due to the dehydrolysis nature of the hydrothermal process, hydroxyl groups could remain inside and/or on the surface of the films. The remaining hydroxyl groups could act as defects, 28,29 which affect crystalline structure and electrical properties of BFO thick films. The absence of hydroxyl defects in our BFO thick film, therefore, implies a negligible effect of hydroxyl defects on the leaky electric properties of BFO thick films.…”