**1. Introduction**

Piezoelectricity is a coupling between a material's mechanical and electrical response. In the simple term, when pressure is applied to a piezoelectric material, an electric charge collects on its surface. On the other hand, when field is applied to a piezoelectric material, it mechanical‐ ly deforms [1]. This behavior of piezoelectric materials is widely utilized in optics, astronomy,

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fluid control, and precision machining due to their high generative force, accurate displace‐ ment, and rapid response [2, 3].

To date, most of the commonly used piezoelectric materials are lead-based, such as lead zirconate titanate (PZT) and its solid solutions. Lead-containing materials display high piezoelectric coefficients, especially near the morphotrophic phase boundary (MPB) and have dominated the market of piezoelectric industry [1, 4, 5]. However, the hazardous lead content present within these materials raise serious environmental problems. Therefore, environmen‐ tal issues such as regulations and policies against lead-based materials have been increasingly enacted throughout the world [6–8]. In order to circumvent the drawback of lead toxicity, extensive research is focused on the quest for alternate piezoelectric materials. Numerous research efforts have been devoted to the candidate lead-free piezoelectric materials such as BaTiO3 (BT), K0.5Na0.5NbO3 (KNN), and Bi0.5Na0.5TiO3 (BNT) because of their interesting electromechanical properties. The BT-based ceramics are interesting from the view point of their good ferroelectricity, chemical, and mechanical stability along with easy processing in polycrystalline form [9, 10]; however, they are inadequate for device applications due to their low Curie temperature (*T*<sup>c</sup> ≈ 120°C) [11, 12]. Alternatively, The KNbO3–NaNbO3 solid solution or the (K,Na)NbO3 (KNN)-based material exhibits good piezoelectric properties as well as high *T*<sup>c</sup> ≈ 420°C and have been studied as substitutes for PZT-based ceramics [13–16]. Nevertheless, alkali metal elements present in KNN-based ceramics easily evaporate at high temperatures. Moreover, KNN ceramics are not only hygroscopic but also make transition between ortho‐ rhombic and tetragonal structure (TO–T) around 200°C, and this transition temperature shifts toward room temperature (RT) with change in composition through doping or substituting other element, which hinders KNN-based ceramics from practical applications [17, 18]. As one of the most feasible lead-free candidates, BNT-based solid solutions have good piezoelectric properties, excellent reproducibility, and high maximum dielectric constant temperature (*T*<sup>m</sup> 300°C) [19–22]. However, poling of pure BNT ceramics is difficult due to their large coercive field (*E*c ~ 73 kV/cm), which is overcome by certain amount through compositional modifica‐ tion and texture development [22–25].

In the recent years, extraordinarily large strain has been reported in compositionally designed BNT-based ceramics [20, 21, 26, 27], which seems to be alternative for PZT in specific actuator applications. Beside, compositional design, texture engineering of polycrystalline ceramics is inimitable and vibrant approach to enhance the piezoelectric properties of ceramics without any major change in the base compositions. Several texture development techniques, such as templated grain growth (TGG) [28], reactive TGG (RTGG) [18], oriented consolidation of anisometric particles [29], screen printing [30], multilayer grain growth [31], and directional solidification technology [32], have been employed to improve the electromechanical proper‐ ties of piezoelectric ceramics. Among all these techniques, RTGG is more suitable for the texture development of perovskite-type materials [33, 34]. In this process, the plate-like template particles that have specific microstructure and crystallographic characteristics are oriented in a matrix ceramic powder through a tape-casting process, and then the consequent heat treatment results in the nucleation and growth of desired crystals on aligned template particles to bring into being textured ceramics [35]. Because of the grain orientation effect induced by templates particles through RTGG process, textured ceramic samples can be more easily poled and thus deliver much higher dielectric and piezoelectric response in comparison with non-textured counterparts prepared by a conventional mixed oxide (CMO) routes [18, 33, 34].

For texture development of BNT-based ceramics, simple BNT templates are considered the most promising because of their large size and plate-like nature. Nevertheless, BNT templates prepared by CMO route have equiaxial morphology which cannot satisfy the requirement as seed in the RTGG process. An alternative convenient approach is to synthesize plate-like perovskite templates by a topochemical microcrystal conversion (TMC) process. This process involves substitution or modification of the interlayer cations, however, retaining the struc‐ tural and morphological features of plate-like layered-perovskite precursors by ion exchange and intercalation reactions at low temperatures [36, 37]. Considering the importance of BNTbased ceramics, this chapter describes the synthesis of BNT particles by different techniques; CMO route along with TMC methods followed by fabrication of BaZrO3-modified BNT ceramics with a chemical composition of 0.994Bi0.5Na0.5TiO3–0.006BaZrO3 (BNT–BZ) by a conventional solid-state reaction method, its texture development by RTGG method using BNT templates, and comparison of the structural and electromechanical properties of the textured and non-textured BNT-BZ ceramics.
