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.