Synthesis and Characterization of Na₂Ti₆O₁₃ Whiskers and their Transformation to (1−x) Na_0.5Bi_0.5TiO₃–xBaTiO₃ Ceramics

Abstract

In this paper we report the synthesis of monoclinic Na2Ti6O13 whiskers and their transformation to lead‐free 0.93Na1/2Bi1/2TiO3–0.07BaTiO3 (NBTBT) ceramics. Synthesis of Na2Ti6O13 templates was performed using molten salt synthesis method. These whiskers were further characterized using XRD, SEM, TEM, and HR‐TEM for structural analysis. Tape‐casting method was used to align the whiskers in base matrix powder and subjected to various processing temperatures to elucidate the microstructure and texture evolution. For this, SEM, HR‐TEM, AFM, and EDS analysis were used as principal tools. The sintering process can be understood by dividing it into three stages, namely (i) transformation of monoclinic whiskers in to NBTBT perovskite phase through topochemical reaction (<800°C), (ii) localized sintering confined on single whisker (800°–1050°C), and (iii) liquid‐phase sintering as densification and grain growth occurs in the whole matrix (>1050°C). The concentric growth ledges observed on grain surfaces were found to be preferably confined on the corners of cubical grains indicating 〈111〉 growth direction. The Lotgering factor (f100) for the sintered matrix was found to decrease with increase in sintering temperature. The longitudinal piezoelectric constant (d33) of samples sintered for 20 h at 1175°, 1200°, and 1225°C was measured to be ∼153, ∼216, and ∼180 pC/N, respectively.

Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

“…The defect-free coherent interface is an important factor for achieving enhanced piezoelectric response15. In NBT based systems, a liquid phase mechanism dominates the sintering process, facilitating mass transport during growth of textured grains1520. The growth of textured grains could be explained by an Ostwald ripening-like process, where larger grains (seed crystals) grow at the expense of smaller ones (matrix grains) because of a difference in surface energy21.…”

Bismuth Sodium Titanate Based Materials for Piezoelectric Actuators

“…In 2011, Maurya, et al [129] use Na 2 Ti 6 O 13 template whiskers prepared by molten salts for the preparation of textured BNT-7 mol % BaTiO 3 ceramics. Figure 12 shows a single tape of matrix containing well-aligned Na 2 Ti 6 O 13 template whiskers.…”

“…SEM image a single tape containing well-aligned Na 2 Ti 6 O 13 template whiskers embedded in the base matrix powder [129]. …”

Enhanced piezoelectricity and nature of electric-field induced structural phase transformation in textured lead-free piezoelectric Na0.5Bi0.5TiO3-BaTiO3 ceramics

“…8 Out of the various possibilities, lead-free (Na 0.5 Bi 0.5 TiO 3 )-BaTiO 3 (NBT-BT) system has emerged as a potential candidate to replace lead-based piezoelectric systems. [9][10][11] The phase transformation behavior of NBT and its solid solutions with BT as a function of E-field has been investigated recently in many studies. Different variants of phase diagrams for NBT-BT have been proposed that consists of ferroelectric rhombohedral and tetragonal phases as end components and an antiferroelectric or ferrielectric orthorhombic components as an intermediate phase.…”