摘要:BaTiO3（BT）是发现最早的无铅压电陶瓷，也是最先获得应用的压电陶瓷材料。然而，由于BT陶瓷的居里温度较低（TC约120℃），压电性能不足（d33约190pC/N），目前BT基陶瓷主要作为介电材料应用（如多层陶瓷电容器），作为压电应用已不多见。近年来，人们对BT基无铅压电陶瓷给予了高度关注。本实验通过传统的固相反应法，在1450℃-1510℃的温度、烧结2小时制备了无铅压电陶瓷xBaTiO3-yCaTiO3-(1-x-y)BaZrO3。研究了xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的相结构和电学性能，探讨了烧结温度、组成对xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷致密度的影响及极化条件对其电学性能的影响。不同温度烧结的、不同组成的xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的主晶相都是钙钛矿结构。随着CT含量的增加，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的晶体结构从赝立方相向四方相转变。xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的电阻率达到了109Ωm数量级，显示了较好的绝缘性能。xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷呈现接近正常铁电体的介电响应峰，但是由于三元固溶体的形成，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的介电响应峰存在明显的宽化现象。xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷呈现饱和对称的电滞回线，随着Ca含量的增加及Zr含量的减少，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的剩余极化强度Pr与矫顽场EC逐渐增加。随着Ca含量的增加与Zr含量的减少，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的居里温度逐渐升高，但总体偏低（未超过120℃）。随着极化电场的升高，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的压电性能随之升高。当极化电场为2.5kV/mm时，xBaTiO3-yCaTiO3-(1-x-y)BaZrO3陶瓷的压电性能基本达到最大值。
关键词：钙钛矿结构；BaTiO3；压电性能；居里温度
Abstract:BaTiO3 (BT) is the earliest discovered lead-free piezoelectric ceramics and the first applicable piezoelectric ceramic materials. However, due to the low Curie temperature (TC is about 120℃), and the relatively poor piezoelectric properties (d33 is about 190pC/N), BT-based ceramics are mainly used as dielectric materials applications (such as multilayer ceramic capacitors). As comparison, it has been rare to be used as the piezoelectric materials. In recent years, the BT-based lead-free piezoelectric ceramic is given high-level attention. In this study, the lead-free xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 piezoelectric ceramics are prepared by the conventional solid-state reaction method sintered at 1450℃-1510℃ for 2 hours. Crystal structure and electrical properties of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics were studied. The influences of sintering temperature and composition on the phase formation and density, and the impact of polarization conditions on the electrical properties of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics were researched. The synthesized xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics exhibit perovskite structure with slight content of impurity. With the increase of the CT content, the crystal structure of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics changes gradually from pseudo cubic phase to tetragonal phase. The resistivity of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics reaches the magnitude of 109Ωm, indicating the excellent insulated performance of the synthesized ceramics. The xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics exhibit dielectric response character nearly similar to that of the normal ferroelectrics, but the dielectric peaks are obviously broaden due to the formation of the ternary solid solution. The xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics exhibit symmetric and saturated P-E hysteresis loops. With the increase of Ca content and the decrease of Zr content, the values of remnant polarization Pr and coercive field Ec increase gradually. The Curie temperature of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics also increases gradually with the increase of Ca content and the decrease of Zr content, but the Curie temperature is still less than 120℃. With the increase of the polarization electric field, the piezoelectric properties of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics increase greatly. When the polarization electric field is 2.5kV/mm, piezoelectric constant d33 of most compositions of the xBaTiO3-yCaTiO3-(1-x-y)BaZrO3 ceramics exhibit the maximum values.
Keywords: perovskite structure; BaTiO3; piezoelectric properties; Curie temperature
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