Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La3+-Doped KNN Lead-Free Ceramics

Yang, Xu; Wang, Lingzhi; Luo, Li; Wu, Wenjuan; Wu, Bo; Li, Junjie; Li, Jie; Zeng, Tixian; Xia, Gengpei

doi:10.3390/nano16020149

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Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics

by

Xu Yang

^1,2,

Lingzhi Wang

^1,2,

Li Luo

^1,2,*,

Wenjuan Wu

^1,2,*,

Bo Wu

³,

Junjie Li

^1,2

,

Jie Li

^1,2,

Tixian Zeng

^4,5 and

Gengpei Xia

⁶

¹

Sichuan Province Key Laboratory of Information Materials and Devices Application, College of Optoelectronic Engineering (Chengdu IC Valley Industrial College), Chengdu University of Information Technology, Chengdu 610225, China

²

Sichuan Meteorological Optoelectronic Sensor Technology and Application Engineering Research Center, Chengdu University of Information Technology, Chengdu 610225, China

³

Sichuan Province Key Laboratory of Information Materials, Southwest Minzu University, Chengdu 610041, China

⁴

Dazhou Industrial Technology Research Institute, Dazhou 635000, China

⁵

CMA Key Laboratory of Cloud-Precipitation Physics and Weather Modification, Beijing 100081, China

⁶

Chengdu Product Quality Inspection and Research Institute Co., Ltd., Chengdu 610199, China

^*

Authors to whom correspondence should be addressed.

Nanomaterials 2026, 16(2), 149; https://doi.org/10.3390/nano16020149 (registering DOI)

Submission received: 16 December 2025 / Revised: 15 January 2026 / Accepted: 20 January 2026 / Published: 22 January 2026

(This article belongs to the Special Issue Nanostructured Materials for Electric Applications)

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Abstract

Lead-free transparent ferroelectric ceramics with integrated opto-electro-mechanical functionalities are pivotal for next-generation multifunctional devices. In this study, K_0.48Na_0.52NbO₃-xLa₂O₃ (KNN-xLa, x = 0.005 − 0.04) ceramics were fabricated via a conventional solid-state route to investigate the La³⁺-induced multiscale structural evolution and its modulation of optical and electrical properties. La³⁺ substitution drives a critical structural transition from an anisotropic orthorhombic phase (Amm2) to a high-symmetry pseudocubic-like tetragonal phase (P4mm) for x ≥ 0.025, characterized by minimal lattice distortion (c/a = 1.0052). This enhanced structural isotropy, coupled with submicron grain refinement (<1 μm) driven by -mediated solute drag, effectively suppresses light scattering. Consequently, a high-transparency plateau (T₇₈₀ ≈ 53–58%, T₁₇₀₀ ≈ 70–72%) is achieved for 0.025 ≤ x ≤ 0.035. Simultaneously, the system undergoes a crossover from normal ferroelectric (FE) to relaxor (RF) state, governed by an FE–RF boundary at x = 0.015. While x = 0.005 exhibits robust piezoelectricity (d₃₃ ≈ 92 pC/N), the x = 0.015 composition facilitates a transitional polar state with large strain (0.179%) and high polarization (P_m ≈ 33.3 μC/cm², P_r ≈ 15.8 μC/cm²). Piezoresponse force microscopy (PFM) confirms the domain evolution from lamellar macro-domains to speckle-like polar nanoregions (PNRs), elucidating the intrinsic trade-off between optical transparency and piezoelectricity. This work underscores La³⁺ as a potent structural modifier for tailoring phase boundaries and defect chemistry, providing a cost-effective framework for developing high-performance transparent electromechanical materials.

Keywords: lead-free transparent ferroelectric ceramics; potassium sodium niobate; La³⁺ doping; nanoscale structural engineering; multifunctional properties

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MDPI and ACS Style

Yang, X.; Wang, L.; Luo, L.; Wu, W.; Wu, B.; Li, J.; Li, J.; Zeng, T.; Xia, G. Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics. Nanomaterials 2026, 16, 149. https://doi.org/10.3390/nano16020149

AMA Style

Yang X, Wang L, Luo L, Wu W, Wu B, Li J, Li J, Zeng T, Xia G. Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics. Nanomaterials. 2026; 16(2):149. https://doi.org/10.3390/nano16020149

Chicago/Turabian Style

Yang, Xu, Lingzhi Wang, Li Luo, Wenjuan Wu, Bo Wu, Junjie Li, Jie Li, Tixian Zeng, and Gengpei Xia. 2026. "Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics" Nanomaterials 16, no. 2: 149. https://doi.org/10.3390/nano16020149

APA Style

Yang, X., Wang, L., Luo, L., Wu, W., Wu, B., Li, J., Li, J., Zeng, T., & Xia, G. (2026). Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics. Nanomaterials, 16(2), 149. https://doi.org/10.3390/nano16020149

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Multiscale Structural Modulation and Synergistic Enhancement of Transparency and Relaxor Behavior in La³⁺-Doped KNN Lead-Free Ceramics

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