锶掺杂二钛酸钡的熔盐法制备及其介电性能

Synthesis of strontium-doped barium dititanate and its dielectric properties by molten salt method

为了获得织构化的二钛酸钡陶瓷,并利用元素替代调控和改善陶瓷介电性能的特点,采用熔盐法,以碳酸钡,二氧化钛和碳酸锶为原料,以氯化钠和氯化钾为熔盐,在840℃反应5h,X射线衍射结果显示,得到的粉体为单相,说明锶离子完全进入了二钛酸钡晶格,成功制备出了摩尔比为1%锶掺杂的二钛酸钡粉体.通过扫描电子显微镜形貌分析显示,制备的二钛酸钡锶单晶颗粒呈棒状,长约2.0μm,矩形截面宽约为100～200nm.棒状颗粒所组成的粉体经单轴压力压片、烧结后得到的二钛酸钡锶陶瓷,居里温度约为415℃,说明当锶掺杂量为1%(摩尔比)时,相比未掺杂的单晶二钛酸钡的居里温度略有降低.在测量频率为10kHz～10MHz的范围内,陶瓷片在成型时压力轴垂直方向上的介电常数峰值约是平行方向上介电常数峰值的3倍,说明陶瓷的介电性能具有明显的各向异性,成功获得了织构化的二钛酸钡锶陶瓷.

Abstract. To obtain textured barium dititanate ceramics and tailor the dielectric properties, 1% （mole ratio） strontium-doped barium dititanate powders were successfully synthesized at 840 ℃ for 5 hours by molten salt method, with barium carbonate, strontium carbonate and titanium dioxide as precursors, sodium chloride and potassium chloride as mixed salts. The X-ray diffraction shows that the products are in single phase, indicating that the strontium ions entered the lattice of barium dititanate. Morphology analysis by scanning electron microscopy shows that the obtained single crystal particles are rod-shaped with a rectangular cross section, up to 2.0 um in length and about 100-200 nm in width. After the particles being pressed with an uniaxial pressure into pellets and sintered subsequently, textured ceramics were successfully fabricated, they show significant anisotropic dielectric properties with the ferroelectric Curie temperature about 415℃ ,which is a little lower than that of non-doped barium dititanate. At differernt frequencies ranging from 10 kHz to 10 MHz, the maximum dielectric constant measured in the direction perpendicular to the forming pressure is three times larger than in the parallel direction.