Donor doping of K 0.5 Na 0.5 NbO 3 ceramics with strontium and its implications to grain size, phase composition and crystal structure

Effects of strontium doping on microstructure and functional properties of solution-derived potassium sodium niobate thin films

“…In contrast, the microstructures of about 240 nm and 230 nm thick KNN F -0.5Sr and KNN F -1Sr films reveal more uniform size distributions and decrease in average grain size to the values of 55.9 nm and 45.6 nm, respectively. The observed narrower grain size distribution and lower value [14][15][16]. The thickness of the KNN F -2Sr was even lower (210 nm) with average grain size of 39.7 nm; however, a porous microstructure was typical for this composition.…”

Microstructure evolution and electromechanical properties of (K,Na) NbO3‐based thick films

“…We relate the unit cell contraction to the variation in the chemical composition of the perovskite phase which could vary with the temperature due to the alkali losses and the formation of the tungsten bronze phase. 16,27 Popovič et al 16 showed that the vapor pressure of potassium over niobate is higher than that of sodium over niobate, that is, 2 and 0.6 mPa, respectively, at 927°C and it increases with temperature. The preferential volatility of potassium from the niobate could lead to the small deviation in K:Na ratio in the thick film.…”

“…It was shown that the TB phase is of the type K 5.75 Nb 10.85 O 30 and it contains only minor amount of sodium ions. 27 Therefore, it can be assumed that due to the alkali loss and the formation of TB phase the K:Na ratio in the perovskite phase is not 1:1 but slightly lower, that is, (1−x): 1. Since the ionic radii of K + is larger than that of Na + , that is, 0.164 and 0.139 nm, respectively, for CN = 12, 28 the unit cell of the perovskite phase decreased.…”

Heterogeneity Challenges in Multiple-Element-Modified Lead-Free Piezoelectric Ceramics

“…Nonetheless, different piezoelectric coefficients have been reported for this composition [11,12], which suggests that the distribution of element species, their possible segregation or inability to incorporate into the structure, and the formation of secondary phases, are all likely to have a major impact on the piezoelectric performance. Studies of the chemical inhomogeneity and secondary phases can be found for single-or a-few-elements-doped KNN [13][14][15][16], while for multiple-elements-modified systems there is a lack of literature data, especially down to the nano and atomic levels.…”