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以氢氧化钾(KOH)和五氧化二铌(Nb2O5)为原料,通过微波水热法在200℃下合成出具有不同晶相、形貌的铌酸钾粉体(KNbO3).当KOH浓度在10~14mol/L时,可以制备出纯相的KNbO3粉体.X射线衍射(XRD)、场发射扫描电镜(FESEM)和透射电镜(TEM)分析可知,KOH浓度由10mol/L增大到15mol/L时,KNbO3粉体由斜方六面体变为正交相,再转变为四方相,对应的形貌也由金字塔状变为棒状,再转变为立方状.当KOH浓度增大到15mol/L时,出现了Nb2O5杂相.常压烧结制备了KNbO3陶瓷,其介电常数达到302,介电损耗为0.023,压电常数达到80 pC/N,平面机电耦合系数为0.17,机械品质因数为70,居里温度为420℃,正交?四方相变温度为223℃.
Potassium niobate powder (KNbO3) with different crystalline phases and morphologies was synthesized by microwave hydrothermal method at 200 ℃ with potassium hydroxide (KOH) and niobium pentoxide (Nb2O5) The pure KNbO3 powder can be prepared at 10 ~ 14mol / L. XRD, FESEM and TEM analysis show that the KOH concentration increases from 10mol / L to 15mol / L, the KNbO3 powder changed from rhombohedral to orthorhombic phase, and then transformed into tetragonal phase, the corresponding morphology changed from pyramid to rod shape and then into cubic shape.When KOH concentration was increased to 15mol / L , The Nb2O5 heterophasic phase appeared.The KNbO3 ceramics were prepared by atmospheric pressure sintering, the dielectric constant of which reached 302, the dielectric loss of 0.023, the piezoelectric constant of 80 pC / N, the plane electromechanical coupling coefficient of 0.17 and the mechanical quality factor of 70 , The Curie temperature is 420 ℃, the orthorhombic tetragonal phase transition temperature is 223 ℃.