Comprehensive investigation of structural, dielectric and local piezoelectric properties of KNN ceramics

Abstract

In this research paper, we utilized the traditional high-temperature solid-state reaction method to fabricate the K[Formula: see text]Na[Formula: see text]NbO3, K[Formula: see text]Na[Formula: see text]NbO3 and K[Formula: see text]Na[Formula: see text]NbO3 (abbreviated as KNN-1, KNN-2, and KNN-3, respectively) lead-free ion deficient ceramics for understanding the influence of ionic deficiency on the crystalline structure and dielectric/piezoelectric properties of the samples. X-ray diffraction patterns of these samples exhibited a perovskite tetragonal phase. Dielectric anomalies around 287∘C and 471∘C were identified as ferroelectric to ferroelectric and ferroelectric to paraelectric-transition temperatures for KNN-2 at 1[Formula: see text]kHz. It was found that the composition KNN-2 exhibit relatively high Curie temperature i.e., 471∘C. The conductivity plots confirm that the activation energies are frequency-dependent. The impedance behavior in our ceramic samples can be analyzed with the bulk/grain effect. The slope of [Formula: see text] with temperature shows negative temperature coefficient of resistance (NTCR) type behavior in proposed KNN ceramics material.

Eu-doped K0.5Na0.5NbO3-(Ba,Sr)TiO3: A novel lead-free luminescent ferroelectric transparent ceramic with reversible photochromism

“…Environment-friendly lead-free KNN-based ceramics have been regarded as the most promising alternative to toxic lead-based piezoelectric materials, owing to their moderate dielectric constant, optimum piezoelectric response and good ferroelectricity. [8][9][10][11][12][13] Recently, RE-doped KNN ceramics have been verified to have both PC and PL modulation behaviors induced by vacancy-related defects (e.g., K/Na/O vacancies), [2][3][4][5][6][7] expanding the electrical applications to optoelectronic areas. Generally, pure KNN ceramics own poor relative density ($95%), low symmetry structure (orthorhombic phase) and large grain size (1-2 m).…”

Sodium Potassium Niobate-Based Piezoelectrics Sintered in Humid Air

“…The peak at 23° 2θ is LiNbO3 [40], while the peaks at approx. 28°, 33° and 35° 2θ are commonly found in KNN-based samples and most likely correspond to K3Li2Nb5O15 [41] or K2Nb6O16 [14,42]. The intensity of the secondary phases is lower after sintering (Fig.…”

Piezoelectrically enhanced photocatalysis of KxNa1−xNbO3 (KNN) microstructures for efficient water purification

“…29 Recently, researchers have found that antiferroelectric-type NaNbO 3 could be dissolved into ferroelectric-type KNbO 3 to form a single-phase solid solution K 1−x Na x NbO 3 (KNN). 30,31 Better piezoelectric properties of KNN materials were demonstrated by Saito et al 32 who prepared hexa-membered ceramics with piezoelectric constants as high as 416 pC/N, which was comparable to the conventional lead-containing piezoelectric material PbZr x Ti 1−x O 3 . Therefore, KNN materials might have a better piezo-photocatalytic performance than pure NaNbO 3 or KNbO 3 .…”