Xie Shaoxiong, Xu Jiageng, Chen Yu, Tan Zhi, Nie Rui, Wang Qingyuan, Zhu Jianguo
College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China.
Materials (Basel). 2018 Mar 27;11(4):503. doi: 10.3390/ma11040503.
A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi₄TiWO + 0.2 wt % Cr₂O₃, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi₂Ti₂O₇ grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall-Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase.
一种钨/铬（W/Cr）共掺杂钛酸铋（BIT）陶瓷（Bi₄TiWO + 0.2 wt% Cr₂O₃，简称为BTWC）通常在1050至1150°C之间烧结，并且已经通过纳米压痕和微压痕技术研究了在不同温度下烧结的陶瓷的压痕行为和力学性能。首先，在BTWC陶瓷中或多或少发现了作为第二相的Bi₂Ti₂O₇晶粒，并且陶瓷的晶粒尺寸随着烧结温度的升高而增大。对BTWC陶瓷的纳米压痕测试表明，陶瓷的测试硬度随着烧结温度的升高而降低，这可以用霍尔-佩奇方程来解释，并且可以根据考虑压痕尺寸效应的压力-状态-响应（PSR）模型计算真实硬度，其中硬度值取决于载荷大小。然而，在使用微米尺寸的维氏压头时，在较低温度（1050°C）下烧结的样品产生了四条线性扩展的裂纹，但是，在较高温度（1125°C）下烧结的样品中观察到这些裂纹缩短了。此外，在后者中同时存在裂纹偏转和裂纹分支。BTWC陶瓷的硬度和断裂韧性随着烧结温度的升高呈现出相反 的变化趋势。较高的烧结温度往往会导致较低的硬度和较高的断裂韧性，这分别可归因于粗晶粒更容易发生塑性变形和更强的裂纹抑制作用，以及第二相带来的增韧效果。
