3D printed Er3+ doped KNNLN piezoelectric ceramics for transparent ultrasonic transducer application

The transparent [Li-0.04(K0.5Na0.5)(0.96)]NbO3+0.5mol% Er2O3 (KNNLN-Er) lead-free piezoelectric ceramics were prepared by stereolithography technique. The influence of different sintering holding time (4h similar to 8h) on the micromorphology, relative density, shrinkage, electric properties, and photoluminescence properties were systematically investigated. The KNNLN-Er ceramics show the coexistence of orthorhombic and tetragonal structures. The grain size increases obviously and then decreases slightly with the holding time increasing. The KNNLN-Er ceramics exhibit good piezoelectric performance (piezoelectric constant d(33)similar to 97 pC/N, electromechanical couple coefficient k(t)similar to 0.36) and the moderate transparency of 34% when the holding time is 6h during sintering at 1120 degrees C. Besides, the intensity of the photoluminescence emission spectra increases with the holding time increasing. Furthermore, in order to estimate the properties of the KNNLN-Er transparent ceramics, an ultrasonic transducer with a center frequency of 10.5 MHz was fabricated, which can be used for photoacoustic and fluorescence imaging. The results indicate that the KNNLN-Er ceramics have potential for multimode imaging applications.