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Detailed Program
Paper Number : LP-O03
Time Frame : 11:35~11:47
Presentation Date : Friday, 28, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : Wook Jo
Session Chair 2# : Wataru Sakamoto
Evaluation of single crystal growth behaviour of (K0.5Na0.5)NbO3-SrTiO3 lead free piezoelectric ceramics grown by the solid state crystal growth (SSCG) method
Muhammad Umer FAROOQ
Chonnam National University
Keywords: lead free piezoelectric material, single crystal growth, microstructure

Lead free piezoelectric ceramics are being developed due to concerns over the health issues of high lead content in conventional lead zirconate titanate piezoelectric ceramics. However, their piezoelectric properties are as yet inferior to those of Pb(Zr,Ti)O3. In order to improve their piezoelectric properties, single crystal growth of lead-free piezoelectric ceramics is being actively studied. Single crystals of (K0.5Na0.5)NbO3 (KNN) based ceramics have good piezoelectric properties but conventional crystal growth techniques require specialized furnaces and expensive Pt crucibles. The solid state crystal growth (SSCG) method has been employed to grow single crystals of lead free KNN based ceramics owing to its ease of processing and use of relatively low cost equipment.
In the present work, the single crystal growth by SSCG of (100-x)(K0.5Na0.5)NbO3-xSrTiO3 (KNN-ST), where x= 0,1,2,3 has been examined. Powders are prepared by the conventional mixed oxide method. XRD analysis is performed to verify the single phase perovskite structure of the powders. A <001> KTaO3 seed crystal is buried in the center of the powders and pressed into a pellet. These pellets are then sintered at 1100oC for 1h, 3h, 5h and 10h. A single crystal of the ceramic composition grows onto the seed. Samples are vertically sectioned using a low speed diamond wheel saw, polished, thermally etched and the microstructure examined by Scanning Electron Microscopy. For the KNN sample, both single crystal growth and abnormal grain growth in the matrix begin to take place within one hour. As the amount of SrTiO3 in the KNN-ST solid solution increases, the onset of both single crystal growth and abnormal grain growth are delayed. The effect of SrTiO3 addition on the single crystal and matrix grain growth behavior is explained in terms of the interface reaction-controlled theory of grain growth.
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