Preparation and characterization of Mn-doped Li0.06(Na0.5K0.5)0.94NbO3 lead-free piezoelectric ceramics with surface sol-gel coatings

Abstract

This study investigated the effects of Mn doping and sol-gel surface coating on the structural and the electrical properties of lead-free Li0.06(K0.5Na0.5)0.94NbO3(LNKN) ceramics in disc form for use as eco-friendly piezoelectric devices. The 1-mol% Mn-doped LNKN ceramic showed a relatively high piezoelectric constant owing to its high density in the case of its being annealed at a temperature of 1010 • C. A Mn-doped LNKN sol-gel solution with the same composition as that of the ceramics was spin-coated and sintered on both sides of the ceramic surfaces to acquire improved electrical properties. The sol-gel surface coating could play a decisive role in filling the pores, resulting in flat and stable interfaces between the electrodes and the piezoelectric elements. As a result, the highest piezoelectric constant, d33, of 173 pC/N could be obtained for the Mn-doped LNKN ceramics with 420-nm-thick sol-gel surface coatings.