Tuning the Piezoelectric Performance of K_0.5Na_0.5NbO₃ through Li Doping: Insights from Structural, Elastic and...

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Potassium sodium niobate (KNN) is a lead-free piezoelectric ceramic with potential applications.
• Understanding the impact of doping on KNN properties is crucial for optimizing its performance.

Purpose of the Study:

• To investigate the structural, elastic, piezoelectric, and electronic properties of Li-doped KNN (KNN-L).
• To correlate these properties with Li-doping concentration and substitution sites.
• To identify optimal doping strategies for enhanced piezoelectricity.

Main Methods:

• First-principles calculations were employed to simulate and analyze the properties of KNN-L.
• Systematic variation of Li-doping content and its effect on atomic structure.
• Evaluation of elastic moduli, hardness, Poisson ratio, and electronic band structure.

Main Results:

• Li-doping generally increases bulk modulus, shear modulus, Young's modulus, and hardness compared to pristine KNN.
• The Poisson ratio decreases with Li-doping, indicating reduced ductility.
• All doped structures exhibit direct band gap semiconducting behavior.
• K$_{0.5}$Na$_{0.375}$Li$_{0.125}$NbO$_{3}$ shows the highest piezoelectric charge constant (d$_{33}$ = 44.72 pC/N), a 1.5-fold improvement over KNN.

Conclusions:

• Li-doping effectively modifies the structural, elastic, and electronic properties of KNN.
• The enhanced piezoelectric performance in KNN-L is attributed to the interplay of elastic and electronic property modifications.
• This study highlights Li-doped KNN as a promising lead-free piezoelectric material.