High quality KNN ceramics were prep

采用冷烧结辅助烧结法制备了高质量的KNN陶瓷，并仔细研究了烧结工艺对其组成，微观结构和电性能的影响。与以PVA作为粘合剂压制的生坯相比（理论密度的53％），冷烧结的生坯表现出更高的密度（RD高于65％），并且在烧结后最终密度可以达到近98％程序。TEM和EDS结果表明，在冷烧结过程中，不溶性溶解占主导地位，导致A位阳离子的浸出比B位更快。同时，钾离子的浸出率比钠离子高，并且在冷烧结后在KNN颗粒表面形成了一些富K的非晶态沉淀，它会在随后的烧结过程中转变为K4Nb6O17第二相。同时，<br>增加的生坯密度可以有效降低烧结温度，并大大提高最终产品的烧结密度。K4Nb6O17相的形成和烧结密度的增加可以有效地减少碱金属元素的蒸发（尤其是钾的蒸发），从而改善KNN陶瓷的性能。CSAS生产的陶瓷在1115°C烧结，表现出出色的铁电，压电和介电特性。压电系数，介电常数，10 kHz时的介电损耗，残余极化和矫顽场分别为131pC / N，10922、4.86％，17.3C / cm2<br>和8.3kV / cm。这些值对于没有任何特殊掺杂剂的​​纯KNN系统来说是相当不错的。此外，CSAS技术的另一个令人鼓舞的结果是，人们可以在很宽的烧结温度范围（1055-1145oC）内生产KNN陶瓷而不会牺牲其性能。这可能归因于在相对较低的烧结温度下CSAS程序中致密化的增强，以及在较高的烧结温度下碱挥发的减少。综上所述，CSAS方法可以有效解决KNN陶瓷烧结性差的问题，对高性能KNN基陶瓷的制备有很大帮助。

High quality KNN ceramics were prepared by cold sintering assisted sintering method, and the effects of the sintering process on the composition, microstructure, and electrical properties were carefully investigated. Compared to the green pellets that were pressed with PVA as binder (53% of theoretical density), the cold-sintered green pellets demonstrated an improved density (above 65% R.D.), and the final density can reach to nearly 98% after following sintering procedure. The TEM and EDS results demonstrated that incongruent dissolution was dominant during cold sintering resulting in a faster leaching for A-site cations than B-site. And meanwhile potassium ions had a much higher leaching rate than sodium ions, and formed some K-rich amorphous precipitates on the KNN particle surface after cold sintering, which would transform to K4Nb6O17 second phase during the subsequent sintering process. Meanwhile, the <br>increased green density can effectively lower down the sintering temperature, and greatly increase the sintering density of final products. The formation of K4Nb6O17 phase and the increase of sintering density can effectively reduce the evaporation of alkali elements (especially for potassium), and consequently improve the properties of KNN ceramics. The CSAS produced ceramics sintered at 1115°C exhibited excellent ferroelectric, piezoelectric, and dielectric characteristics. Its piezoelectric coefficient, dielectric constant, dielectric loss at 10 kHz, remnant polarization and coercive field were 131pC/N, 10922, 4.86%, 17.3C/cm2<br>and 8.3kV/cm, respectively. These values are reasonably good for pure KNN system without any special dopants. Moreover, another inspiring result for CSAS technique is that one could produce KNN ceramics in a very wide range of sintering temperature (1055-1145oC) without sacrificing their properties. This may be attributed to the enhancement of densification during CSAS procedure at relatively low sintering temperature, and the reduction of alkali volatilization at high sintering temperatures. To sum up, the method of CSAS could be an effective solution for the problem of poor sinterability of KNN ceramics, and a great help to the fabrication of high-performance KNN-based ceramics.

采用冷烧结辅助烧结方法制备了高质量的KNN陶瓷，研究了烧结工艺对其组成、显微结构和电性能的影响。与以聚乙烯醇（PVA）为粘结剂（理论密度的53%）压制的生球相比，冷烧结的生球密度提高了（R.D.）65%以上，烧结后的最终密度接近98%。TEM和EDS结果表明，在低温烧结过程中，不均匀溶解占主导地位，导致a位阳离子的浸出速度快于B位。同时钾离子比钠离子有更高的浸出率，冷烧结后在KNN颗粒表面形成一些富K的非晶态沉淀，在随后的烧结过程中转变为K4Nb6O17第二相。同时<br>提高生坯密度可以有效降低烧结温度，大大提高成品的烧结密度。K4Nb6O17相的形成和烧结密度的增加可以有效地减少碱元素（特别是钾元素）的挥发，从而改善KNN陶瓷的性能。CSAS制备的陶瓷在1115℃烧结，表现出优异的铁电、压电和介电特性。其压电系数、介电常数、10khz介电损耗、残余极化和矫顽场分别为131pC/N、10922、4.86%、17.3C/cm~2<br>分别为8.3kV/cm。这些值对于纯KNN系统没有任何特殊的掺杂是相当好的。此外，CSAS技术的另一个鼓舞人心的结果是，可以在很宽的烧结温度范围（1055-1145oC）下制备KNN陶瓷，而不牺牲其性能。这可能是由于在较低的烧结温度下CSAS过程中致密化程度的提高，以及在较高的烧结温度下碱挥发程度的降低。综上所述，CSAS法可以有效地解决KNN陶瓷烧结性差的问题，对制备高性能KNN基陶瓷有很大的帮助。<br>