Development and evaluation of KNLNTS-cement composites for use as piezoelectric sensors in structural health monitoring applications

• KNLNTS-cement composites show acoustic impedance ideal for SHM sensor applications. • Dielectric constant and piezoelectric coefficient significantly increase after 14 days of cement hydration. • Piezoelectric coefficient reaches 24.15 pC/N at 70 vol.% KNLNTS ceramic content. • Strong interfacial bonding is observed between KNLNTS ceramics and the cement matrix. • Dielectric loss decreases with increasing KNLNTS content due to ion conduction in the cement. The development of accurate, environmentally friendly piezoelectric sensors is increasingly critical in structural health monitoring (SHM), especially for applications like bridge and tall building vibration monitoring. Traditional piezoelectric materials often suffer from impedance mismatches with concrete, leading to inaccuracies in sensor readings. This study presents a novel complex-ion doped, lead-free KNLNTS ceramic ((Nb₀.₈₄Ta₀.₁₀Sb₀.₀₆)O₃) fabricated for improved SHM applications. Sintered at 1075 °C for 2 h, the KNLNTS ceramics achieved promising properties ( ε r ∼ 1386, tan δ ∼ 0.022, T C ∼ 251 °C, d ₃₃ ∼ 118 pC/N). Using KNLNTS ceramics in cement-based composites (0–3 connectivity) with varying contents (30 %–70 % by volume) of ordinary Portland cement, the study demonstrates that these composites closely match the acoustic impedance of host concrete structures. This impedance compatibility significantly enhances measurement accuracy compared to conventional piezoelectric materials. Detailed investigations of dielectric properties revealed a consistent rise in piezoelectric coefficient (8.40–24.15 pC/N) with increasing KNLNTS content, making these composites suitable for sensitive detection of stress, strain, and cracking in concrete. This work positions KNLNTS-cement composites as highly effective and sustainable piezoelectric sensors for advanced SHM applications.