具有“芯 - 壳”及纳米畴结构的 X9R 型钛酸钡基陶瓷介电性能研究
Design of High-Performance BaTiO 3 -Based X9R Ceramics by Forming a Core-Shell Structure and Nano-Domains
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摘要: 高容高温是下一代片式多层陶瓷电容器的重要发展方向, 因此, 开发具有高容高温特性的 X9R 型钛酸钡基介质材料, 对于促进高容高温多层陶瓷电容器的发展具有重要意义。该研究以钛酸钡(BaTiO 3 , BT)为原料, 利用传统固相反应烧结法, 并通过调节钛酸铋钠(Bi 1/2 Na 1/2 TiO 3 , BNT)的基体固溶量和稀土元素铌(Nb)的掺杂量, 成功制备出具有较高室温介电常数和较宽容温特性的 Nb 掺杂 BT-BNT 介质体系。在此基础上, 对 X9R 型介质材料纳米畴及“芯-壳”结构与介温特性之间的关系进行了研究。实验结果表明, 当 BNT 固溶量为 10 mol%, BT-BNT 的居里温度为 190 ℃, 晶粒具有典型的 90°铁电畴;在 0.9BT-0.1BNT 固溶体中掺杂 2.0 mol% 的 Nb 元素, 介电常数为 1 800, 损耗 <2.0%, 容温系数(-55~200 ℃) ≤ 15%, 晶粒形成明显的“芯-壳”结构, 其中“芯”部具有小尺寸的纳米尺度铁电纳米畴, “壳”部为 Nb 均匀分布的 BT-BNT 固溶体。因此, 0.9BT-0.1BNT-2.0Nb 陶瓷是一种极具前景的 X9R 型多层陶瓷电容器用电介质材料。Abstract: As a key and foundational component for modern electronic devices, the multilayer ceramic capacitors with excellent temperature stability are desirable for the next generation of high-temperature capacitors. Herein, authors fabricated Nd-doped BaTiO 3 -(Bi 1/2 Na 1/2 )TiO 3 dielectric ceramics with Electronic Industries Association specification of X9R by solid-state reaction process. It is shown that the 0.9BT-0.1BNT exhibits a homogeneous solid solution with the ferroelectric domain structure. With an increase in the Nd concentration and temperature, the tetragonality decreases while the peak of dielectric permittivity curve becomes more broaden and stable. In particular, Nb-doped 0.9BT-0.1BNT samples imply a typical core-shell structure with nano-sized domain in the core to increase the dielectric constant. In addition, 0.9BT-0.1BNT-2.0Nb ceramic demonstrates the dielectric constant of 1 800 and dielectric loss of 2.0% from -55 ℃ to 200 ℃. This work not only provides a promising candidate material, but also provides an attractive method to design new family of high-performance dielectric ceramics for high temperature MLCCs applications.