Abstract K 0.5 Na 0.5 Nb 1-x Ta x O 3 (KNNT) (with x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830 °C for 5 h. Subsequent sintering of centimeter size pellets, 1–2 mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x = 0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960 °C, under 50 MPa, for 5–10 min with heating rates of 100 °C/min. High relative permittivity (e r = 1027), piezoelectric charge coefficient (d 33 = 160 pC/N) and piezoelectric coupling factor (k p = 46%) are obtained in spark plasma sintered K 0.5 Na 0.5 Nb 1-x Ta x O 3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.

中文翻译：

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钽取代无铅K 0.5 Na 0.5 Nb 1-x Ta x O 3 陶瓷的复合微结构和压电性能

摘要 K 0.5 Na 0.5 Nb 1-x Ta x O 3 (KNNT) (x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) 陶瓷是通过球磨和两次在 830 °C 下煅烧 5 h 制备的. 使用常规和放电等离子烧结技术在各种条件下研究 1-2 毫米厚的厘米尺寸球团的后续烧结。X 射线衍射和拉曼光谱相鉴定揭示了在约 x = 0.50 处发生的正交到四方相变，与化学无序相关。扫描电子显微镜观察和相关的能量色散 X 射线光谱分析揭示了陶瓷的某些复合方面。用钽代替铌，对应于 x 的增加，显着降低了晶粒尺寸，但也降低了通过常规烧结烧结的陶瓷的致密化，同时，两种烧结技术都观察到压电性能的增强。由于放电等离子烧结工艺的参数优化，温度-时间-压力，相对密度显着提高超过 96%，所有组合物在 920 到 960 °C 之间，在 50 MPa 下烧结 5-10 分钟加热速率为 100 °C/min。在放电等离子体烧结的 K 0.5 Na 0.5 Nb 1-x Ta x O 3 复合材料中获得了高相对介电常数 (er = 1027)、压电电荷系数 (d 33 = 160 pC/N) 和压电耦合因子 (kp = 46%)陶瓷，x 范围在 0.10 和 0.30 之间，并且适用于某些特定的放电等离子烧结条件。因此，铌位点上的钽单元素取代，结合放电等离子烧结，