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<p>Recently, LaNbO<sub>4</sub>-based proton-conducting materials have emerged as promising alternatives to conventional electrolytes, particularly due to their lower sintering temperatures, making them suitable for hydrogen and humidity sensing applications at temperatures below ~ 700&#xa0;°C. However, LaNbO<sub>4</sub> undergoes a structural phase transition from a monoclinic fergusonite to a tetragonal scheelite-type structure at elevated temperatures, which hinders its performance. Controlling this phase transition is, therefore, a critical to enhance proton conduction. The synthesis method plays a pivotal role in stabilizing the phases and optimizing the microstructure of ceramic materials, thereby improving their transport properties. This study demonstrates a novel synthesis of pristine and calcium-doped LaNbO<sub>4</sub> nanocrystals using the microwave hydrothermal (MH) method. X-ray diffraction (XRD) analysis confirms the formation of single-phase monoclinic LaNbO<sub>4</sub> at a significantly lower calcination temperature (800&#xa0;°C for 3&#xa0;h) than conventional methods (~ 1000&#xa0;°C). Calcium doping enhances phase stability and proton conductivity by introducing oxygen vacancies and reducing grain boundary resistance. Impedance analysis further reveals that La<sub>0.99</sub>Ca<sub>0.01</sub>NbO<sub>4</sub> a proton conductivity of 5.23 × 10<sup>‒4</sup> S·cm<sup>‒1</sup> at 700&#xa0;°C, markedly higher than pristine LaNbO<sub>4</sub> (9.5 × 10<sup>‒5</sup> S·cm<sup>‒1</sup>). These findings position La<sub>0.99</sub>Ca<sub>0.01</sub>NbO<sub>4</sub> as a highly promising candidate for hydrogen energy applications.</p>

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Enhanced proton conductivity in low-temperature sintered pristine and Ca-doped LaNbO4 nanocrystals synthesized via microwave hydrothermal method

  • 期刊论文

  • 发表日期：

    2025年3月8日

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  • S. Balasundari,
  • S. Jayasubramaniyan,
  • M. Vithiya,
  • P. A. Rayjada,
  • N. Satyanarayana,
  • T. Rani,
  • P. Muralidharan

摘要

Recently, LaNbO4-based proton-conducting materials have emerged as promising alternatives to conventional electrolytes, particularly due to their lower sintering temperatures, making them suitable for hydrogen and humidity sensing applications at temperatures below ~ 700 °C. However, LaNbO4 undergoes a structural phase transition from a monoclinic fergusonite to a tetragonal scheelite-type structure at elevated temperatures, which hinders its performance. Controlling this phase transition is, therefore, a critical to enhance proton conduction. The synthesis method plays a pivotal role in stabilizing the phases and optimizing the microstructure of ceramic materials, thereby improving their transport properties. This study demonstrates a novel synthesis of pristine and calcium-doped LaNbO4 nanocrystals using the microwave hydrothermal (MH) method. X-ray diffraction (XRD) analysis confirms the formation of single-phase monoclinic LaNbO4 at a significantly lower calcination temperature (800 °C for 3 h) than conventional methods (~ 1000 °C). Calcium doping enhances phase stability and proton conductivity by introducing oxygen vacancies and reducing grain boundary resistance. Impedance analysis further reveals that La0.99Ca0.01NbO4 a proton conductivity of 5.23 × 10‒4 S·cm‒1 at 700 °C, markedly higher than pristine LaNbO4 (9.5 × 10‒5 S·cm‒1). These findings position La0.99Ca0.01NbO4 as a highly promising candidate for hydrogen energy applications.