Our website is currently undergoing maintenance. Article records and full texts remain available. Submissions can be made through the Editorial Manager.

Lead-Free KNN Piezoelectric Stack Actuators for Semi-Active Suspension Control: Correlating Fabrication, Microstructure, and Electromechanical Performance

Yan Duan

Journal of Ceramic Science and Technology, Vol. 17, No. 2 (2026), pp. 167-178

DOI: 10.4416/JCST2025-00040

Download full article (PDF)

Abstract

This study reports on the design, processing, and functional assessment of Li/Sb/Ta-modified (K0.5Na0.5)NbO3 ceramics targeted for environmentally compliant high-force actuators in automotive vibration management. Ten compositions were synthesized on the basis of solid-state reaction with sintering between 1 050 and 1 150 °C, and multi-scale characterization combined in situ high-temperature XRD, SEM, HRTEM, Raman spectroscopy, XPS, EBSD, BET analysis, dielectric spectroscopy, and impedance measurements with actuator-level electromechanical testing. Compositional tuning established an orthorhombic-tetragonal coexistence window in which the benchmark composition (K0.45Li0.05)(Na0.47Li0.03)(Nb0.90Sb0.06Ta0.04)O3 exhibits 58 % orthorhombic and 42 % tetragonal phases, an O-T transition at 195 °C, and a Curie point above 380 °C. At an optimized sintering temperature of 1 100 °C this ceramic reaches a density of 4.59 g/cm3 (99.2 % theoretical), grain sizes of about 2.4 μm, and a specific surface area of 1.2 m2/g, together with εr = 1 850 and tanδ ≈ 2.5 % at 1 kHz. Moderate oxygen vacancy contents around 7.5 % balance grain-boundary softening and insulation, yielding d33 = 432 pC/N, kp = 0.45, Pr = 28.7 μC/cm2, and Ec = 12.4 kV/cm. Long-term reliability is demonstrated by 94.3 % retention of d33 after 1 000 h aging at 85 °C and only 6.8 % degradation after 106 bipolar cycles at 50 Hz. Prototype 10-layer multilayer devices fabricated from the optimized composition show stable displacement response under fields of several kV/mm, confirming the potential of these lead-free ceramics for robust, RoHS-compliant smart suspension hardware. The integrated processing-structure-property correlations established here provide a transferable framework for tuning phase boundaries and defect chemistry in next-generation lead-free actuator ceramics for automotive applications.

Keywords

Phase boundary engineering, relaxor ferroelectricity, defect-mediated conduction, multilayer ceramic devices, automotive vibration isolation

View this issue · Article & DOI index