Citrate complexing sol–gel process of lead-free (K,Na)NbO₃ ferroelectric films

Abstract

The citrate complexing sol–gel process to fabricate lead-free (K,[Formula: see text]Na)NbO3 ferroelectric thin films was studied. Soluble niobium source of niobium–citric acid (Nb–CA) solution was utilized as a raw material to synthesize (K,[Formula: see text]Na)NbO3 thin films, by pyrolyzing at 450–550[Formula: see text]C and annealing at 650[Formula: see text]C. The film pyrolyzed at 450[Formula: see text]C shows poor crystallization with porous morphology, whereas the film pyrolyzed at 550[Formula: see text]C appear to be well-crystallized and denser, and the ferroelectricity was also proved by the [Formula: see text]–[Formula: see text] hysteresis loop measurement.

Local Piezoelectric Behavior of Potassium Sodium Niobate Prepared by a Facile Synthesis via Water Soluble Precursors

“…In the left side micrograph (Figure A), the surface of the post‐heated gel shows the clear presence of pores ascribable to the release of CO 2 gas during the annealing process. The CO 2 evolution is a consequence of the thermal decomposition of the complex oxalates formed through the gelation, as it was already observed by Yao et al and further confirmed by Rani and coauthors . Upon compaction and subsequent annealing at 500 °C, the surface morphology of the final pellet changes with respect to the un‐treated powders.…”

“…The CO 2 evolution is a consequence of the thermal decomposition of the complex oxalates formed through the gelation, as it was already observed by Yao et al and further confirmed by Rani and coauthors. [27,48] Upon compaction and subsequent annealing at 500 C, the surface morphology of the final pellet changes with respect to the un-treated powders. As a consequence of the annealing treatment and uniaxial pressure, evidenced in Figure 3B, the pores definitely disappeared together with a significant crystal growth and the presence of small particles, in agreement with other synthetic procedures.…”

Advanced Synthesis on Lead‐Free KxNa(1−x)NbO3 Piezoceramics for Medical Imaging Applications

“…The gas released during the calcination at 450 C, generated a significant porosity degree with pore dimensions of 10-20 nm. However, the ferroelectric properties were improved only when the system was heated upon 550 C. [97] Dielectric properties could be modulated in KNN system by doping with amphoteric elements. [98] Yttrium, depending on the concentration, can replace ions in the A-or B-site.…”

Lead-Free Ferroelectric Thin Films

“…Chemical solution deposition (CSD) of the KNN-based thin films can be divided according to the alkali metal starting compounds such as acetate based (Kupec et al 2012;Wang et al 2009;Wiegand et al 2013;Yan et al 2010), alkoxide based (mainly ethoxides) (Kang et al 2011;Nakashima et al 2007;Tanaka et al 2007;Yu et al 2013), and only in rare studies non-alcohol niobium salt based (Lu et al 2014;Yao and Zhu 2016). The advantage of the alkali acetate-based over the alkoxidebased method is in the favored crystallization of the single perovskite phase films on platinized silicon substrates at 600-680 C (Čakare-Samardžija et al 2008).…”