In this work, KNNL was sintered as a lead-free alternative to PZT using a pulsed photonic sintering method. The KNNL post-sintering composition remained close to theoretical composition indicating minimal volatilization of alkali metals. Furthermore, a remnant polarization was observed in the processed material. Energy and time demands were greatly reduced using the pulsed photonic sintering method versus conventional furnace sintering.
Piezoelectric materials can produce electric current when bent or compressed. Currently lead zirconium titanate (PZT) is the most widely used piezoelectric material. A promising lead-free alternative is sodium potassium niobate (KNN), which can be doped with lithium (KNNL) to improve its piezoelectric properties. The KNNL formulation used in this study was rod coated onto copper foil. Sintering to promote densification is typically carried out using a furnace at temperatures of around 1000°C for several hours. Furnace sintering is a lengthy and energy-intensive batch process. This work examines the use of pulsed photonic sintering as an alternative sintering process.
A KNNL film sample photonically sintered at 400V, 2 Hz, 20 pulses, 2 cycles and 650 μs pulse length was compared to a pressed pellet sample that was furnace sintered at 1060 °C for 2 h. Both samples showed particles coalescing in SEM images, and therefore were considered to have undergone sintering. A Nb:Na:K elemental composition ratio of 56:20:24 was retained. This is much closer to the theoretical stoichiometric ratio of 51:26:23 than the 61:16:23 ratio seen in the furnace pellet sample. KNNL is prone to volatilization of its Na and K during sintering. This was certainly the case for a sample that was furnace sintered at 700 °C for 2 h and, which had no remaining alkali metals after sintering. The remnant polarization response observed for the photonically sintered film sample was about 0.008 μC/cm2.
An energy consumption study was also carried out to determine the power demand of furnace sintering compared to pulsed photonic sintering. The latter was found to demand 98.1% less energy per unit area of sintered film. Photonic sintering implementation could amount to a significant reduction in cost and energy usage in a large-scale manufacturing setting. Furthermore, photonic sintering required 99.4% less time per unit area of sintered film than furnace sintering in this study, and can be implemented as a high throughput roll-to-roll process.
Sustainable Engineering (MS)
Department, Program, or Center
Industrial and Systems Engineering (KGCOE)
Hernandez Juarez, Sara, "Pulsed Photonic Sintering of Lithium Doped Potassium Sodium Niobate (KNN) for Flexible Energy Harvesting Devices" (2019). Thesis. Rochester Institute of Technology. Accessed from
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