Highly transparent lead-free ceramics of La-doped KNN based were synthesized by conventional solid state reaction method and ordinary sintering process for the first time. The optical and electrical properties of the KNN based lead-free transparent ferroelectric ceramics were investigated in this work. The transparent ceramics exhibited a transparency as high as 60% for the infrared wavelength. Meanwhile, the electrical properties of the ceramics still maintained relatively high levels (d33 = 55 pC/N, Tc = 402 °C), suggesting that it should be a novel and promising lead-free material that used in a large variety of electro-optical devices. [ABSTRACT FROM AUTHOR]