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arXiv · 2510.15139

Morphotropic Phase Boundary (MPB) Induced Enhancement of Ferroelectric and Piezoelectric Properties in Li and Ta modified K0.5Na0.5NbO3

Satyaranjan Sahoo·Dhiren K. Pradhan·Shalini Kumari·Abhisikta Sahu·Koyal Suman Samantaray·Vikas N. Thakur·Anupam Mishra·M. M. Rahaman·Ashok Kumar·Reji Thomas·Philip D. Rack·Dillip K. Pradhan
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Abstract

Lead-free (K0.48Na0.48Li0.04)(Nb1-xTax)O3 (KNLNT-x) ceramics were synthesized to study the effects of Li and Ta substitution on phase transition behavior, microstructure, and ferroelectric, dielectric, and piezoelectric properties. X-ray diffraction and Raman spectroscopy show that compositions with x < 0.10 exhibit a single orthorhombic (Amm2) phase, while 0.10 <= x <= 0.20 show coexistence of orthorhombic and tetragonal (Amm2 + P4mm) phases. For x > 0.20, a single tetragonal (P4mm) phase is obtained. Microstructural analysis shows a dense ceramic with decreasing grain size as Ta concentration increases. Temperature-dependent dielectric studies reveal two transitions: orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC). Both transition temperatures decrease systematically with increasing Ta, and TO-T shifts below room temperature for x > 0.15. The composition KNLNT-0.20 exhibits the highest dielectric constant (Er = 556) and piezoelectric coefficient (d33 = 159 pC/N). The enhanced piezoelectric response is attributed to a morphotropic phase boundary rather than a shift of the polymorphic phase boundary temperature. A composition-temperature phase diagram was constructed based on XRD, Raman, and dielectric data.

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Satyaranjan Sahoo, Dhiren K. Pradhan, Shalini Kumari, Abhisikta Sahu, Koyal Suman Samantaray, Vikas N. Thakur, Anupam Mishra, M. M. Rahaman, Ashok Kumar, Reji Thomas, Philip D. Rack, Dillip K. Pradhan. 2025-10-16. Morphotropic Phase Boundary (MPB) Induced Enhancement of Ferroelectric and Piezoelectric Properties in Li and Ta modified K0.5Na0.5NbO3. https://arxiv.org/abs/2510.15139

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