In Situ Observations of Templated Grain Growth in (Na_0.5K_0.5)_0.98Li_0.02NbO₃ Piezoceramics: Texture Development and Template–Matrix Interactions

Abstract

Nucleation, texture development, and phase equilibria were observed during templated grain growth (TGG) of (Na0.5K0.5)0.98Li0.02NbO3 (NKLN) via in situ X‐ray diffraction (XRD). Initially, NaNbO3 templates and NKLN matrix powder exist as distinct phases with unique lattice parameters. Above 850°C, the templates and matrix begin to react via interdiffusion as characterized by an increase in diffuse scattering between the NaNbO3 and NKLN peaks. This process intensifies immediately prior to template growth, leading to merging of diffraction peaks for these two phases. TGG in this system is thus homoepitaxial in nature as it occurs after the NKLN matrix and NaNbO3 templates form a solid solution. The degree of alignment in the matrix phase is quantified in situ using the March–Dollase parameters r and f. The degree of orientation of the textured NKLN mirrors the initial alignment of the template particles (r ≈ 0.3), while the texture fraction f increases from 0.04 to ~0.67 after 3 h at 1138°C. This increase in texture fraction follows n = 1/3 power law kinetics consistent with liquid‐phase‐assisted normal grain growth on plate‐like templates. As the observed template–matrix interdiffusion and the onset of texture development proceed extremely rapidly, this work demonstrates the utility of in situ XRD for observing details of TGG that cannot easily be seen via ex situ methods.

Using Neutron Diffraction to Investigate Texture Evolution During Consolidation of Deuterated Triaminotrinitrobenzene (d-TATB) Explosive Powder

“…In those efforts, a parameter corresponding to the deformation ratio, λ, is used as a refinement parameter to characterize the observed pole density distribution of the final as-processed microstructure. More recently, Tutuncu et al [53] have used the March-Dollase method to study templated grain growth in situ during sintering of piezoceramic materials.…”

Evolution of textured microstructure of Li-doped (K,Na)NbO3 ceramics prepared by reactive templated grain growth

“…7(b). As is well known, Li-modified KNN and related systems are generally thought to be liquid phase sintering [20,21]. The amorphous morphology pointed by arrow as shown in 11 Fig.…”

“…Meanwhile, the in-situ reaction between NN template particles and KNLN matrix particles occurs when the sintering temperature provides enough activation energy. It is thought that the NN template particles react with the KNLN matrix particles via inter-diffusion and forming a solid solution during in-situ reaction [11,20]. Although the amount of NN phase decreases gradually with the reaction going on, the template particles still retain their plate-like shape and serve as seeds for KNLN phase formation all the time in this stage.…”

“…Temperature dependence of (a) piezoelectric constant d 33 and (b)20 electromechanical coupling factor k t of the textured and nontextured KNLN ceramics.…”

Microstructure development and texture formation in lead-free piezoelectric ceramics prepared by templated grain growth process

“…Because the texture is formed by the elimination of matrix grains, examination of the microstructure development from the green compact to the final sintered compact is important to obtain highly textured ceramics with controlled microstructure, 22) i.e., density, degree of orientation, and grain size. 23) The TGG and RTGG methods are first applied to structure ceramics, 24), 25) and extended to piezoelectric ceramics with the Aurivillius structure, 26),27) tungsten bronze structure, 28), 29) and perovskite structure.…”