OBJECTIVES For the use of partially stabilized zirconia (PSZ) as high-translucent zirconia, the importance of cubic phase (c-ZrO2) is commonly emphasized without much attention for the remaining tetragonal phase (t-ZrO2). The aim is to understand whether the crystal structure and microstructure of t-ZrO2 have paramount influences on the properties of PSZ. METHODS Two grades of 5mol% yttria-stabilized PSZ ceramics were prepared by different processing routes. A 5mol % yttria co-precipitated zirconia (T5Y) was compared with a 3 and 8mol% yttria-stabilized powder mixture grade with a bimodal grain size distribution (B5Y). The phase composition and lattice parameters were studied with x-ray diffraction (XRD) and Rietveld analysis. Mechanical properties were compared in terms of hardness, toughness and biaxial bending strength with Weibull analysis. Their translucency and aging stability were also characterized, and the microstructure before and after aging were followed by scanning electron microscopy (SEM). RESULTS T5Y and B5Y having similar phase composition (about 40% t- and 60% c-ZrO2) showed the same basic properties (density, hardness and toughness), but the lattice parameters of t-ZrO2 and the concomitant microstructure were completely different. The t-ZrO2 phase in T5Y had a higher yttria content and a lower tetragonality (c/a) of 1.0126±0.0002, whereas the t-ZrO2 phase in B5Y was comparable to that in conventional 3Y-TZPs with a tetragonality of 1.0153±0.0002. Consequently, B5Y showed a lower strength with lower Weibull modulus, being less translucent and more aging susceptible as compared to T5Y. The translucency and aging susceptibility of B5Y were even comparable to those of conventional 3Y-TZP. SIGNIFICANCE Not only the phase composition with high cubic phase content but also the lattice parameters and the yttria content in the remaining t-ZrO2 played a determinant role for PSZs to be used as 'high-translucent' zirconia.

中文翻译：

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四方相在高透明性部分稳定的氧化锆中对牙齿修复的重要性。

目的对于使用部分稳定的氧化锆（PSZ）作为高透明氧化锆，通常强调立方相（c-ZrO2）的重要性，而对剩余的四方相（t-ZrO2）却没有太多关注。目的是了解t-ZrO2的晶体结构和微观结构是否对PSZ的性能具有最重要的影响。方法采用不同的工艺路线制备了两种等级的5mol％氧化钇稳定的PSZ陶瓷。将5摩尔％的氧化钇共沉淀氧化锆（T5Y）与具有双峰粒度分布（B5Y）的3摩尔％和8摩尔％的氧化钇稳定粉末混合物进行了比较。通过X射线衍射（XRD）和Rietveld分析研究了相组成和晶格参数。通过威布尔分析比较了机械性能的硬度，韧性和双轴弯曲强度。还对它们的透明度和老化稳定性进行了表征，并通过扫描电子显微镜（SEM）跟踪了老化前后的微观结构。结果具有相似相组成（约40％的t-ZrO2和60％的c-ZrO2）的T5Y和B5Y表现出相同的基本性能（密度，硬度和韧性），但是t-ZrO2的晶格参数和伴随的微观结构完全不同。T5Y中的t-ZrO2相具有较高的氧化钇含量和较低的四方性（c / a）为1.0126±0.0002，而B5Y中的t-ZrO2相与常规3Y-TZP中的四方性为1.0153±0.0002 。因此，与T5Y相比，B5Y显示出较低的强度和较低的威布尔模量，半透明性较低并且更易老化。B5Y的半透明性和老化敏感性甚至可以与常规3Y-TZP相比。意义不仅具有高立方相含量的相组成，而且剩余t-ZrO2中的晶格参数和氧化钇含量都对PSZ用作“高透明”氧化锆起着决定性的作用。