Bonding Optimization Strategies for Flexibly Preparing Multi‐Component Piezoelectric Crystals

Abstract Flexible films with optimal piezoelectric performance and water‐triggered dissolution behavior are fabricated using the co‐dissolution–evaporation method by mixing trimethylchloromethyl ammonium chloride (TMCM‐Cl), CdCl 2 , and polyethylene oxide (PEO, a water‐soluble polymer). The resultant TMCM trichlorocadmium (TMCM‐CdCl 3 ) crystal/PEO film exhibited the highest piezoelectric coefficient (d 33 ) compared to the films employing other polymers because PEO lacks electrophilic or nucleophilic side‐chain groups and therefore exhibits relatively weaker and fewer bonding interactions with the crystal components. Furthermore, upon slightly increasing the amount of one precursor of TMCM‐CdCl 3 during co‐dissolution, this component gained an advantage in the competition against PEO for bonding with the other precursor. This in turn improved the co‐crystallization yield of TMCM‐CdCl 3 and further enhanced d 33 to ≈71 pC/N, exceeding that of polyvinylidene fluoride (a commercial flexible piezoelectric) and most other molecular ferroelectric crystal‐based flexible films. This study presents an important innovation and progress in the methodology and theory for maintaining a high piezoelectric performance during the preparation of flexible multi‐component piezoelectric crystal films.