Tetragonal to Cubic Transformation of SiO₂-Stabilized ZrO₂ Polymorph through Dysprosium Substitutions

Abstract

Partially stabilized tetragonal zirconia (t-ZrO2) is of particular interest for hard tissue replacements. Ageing related failures of the ceramic associated with the gradual transformation from t-ZrO2 to m-ZrO2 (monoclinic zirconia) can lead to its premature removal from the implant site. In addition, monitoring the satisfactory performance of the implant throughout its life span without invasive techniques is a challenging task. The magnetic resonance imaging (MRI) contrast ability of dysprosium (Dy 3+ ) is well established. To this aim, varied levels of Dy 3+ additions in the ZrO2-SiO2 binary oxide system have been explored. The results indicate the effective role of Dy 3+ in the formation of thermally and mechanically stable c-ZrO2 (cubic zirconia) phase at higher temperatures. The presence of SiO2 influenced the t-ZrO2 stabilization whereas Dy 3+ tends to occupy the ZrO2 lattice sites to induce c-ZrO2 transition. Magnetic and magnetic resonance imaging (MRI) tests displayed the commendable contrast ability of Dy 3+ stabilized ZrO2-SiO2 binary systems. Nanoindentation results demonstrate a remarkable enhancement on the mechanical properties.Keywords: Silica; Zirconia; Dysprosium; Stabilization; Mechanical. 3 IntroductionThe demand for bone implants is growing rapidly due to the increasing incidents of trauma and age related defects caused by osteoporosis. In view of the above potential advantages of Dy 3+ as an addition to ZrO2-SiO2 binary oxides in terms of increased t-ZrO2 stability and enhance MRI image contrast, we present a study of the influence of Dy 3+ on the ZrO2-SiO2 binary oxide system through in-situ sol-gel synthesis, followed by a systematic analysis of the resulting phase composition and structure, mechanical strength and imaging contrast features. Materials and Methods Powder synthesisThe synthesis of Dy 3+ doped ZrO2-SiO2 (DZS) binary oxides was achieved through the sol-gel method. Analytical grade Dy(NO3)3.H2O, ZrOCl2·8H2O and (C2H5)4OSi (TEOS), all procured from Sigma-Aldrich, India, were taken as precursors for the synthesis. The molar concentrations of ZrOCl2·8H2O and (C2H5)4OSi were maintained at a constant ratio of 1: 1 throughout the 5 synthesis whereas the Dy(NO3)3 additions were adjusted to obtain a wide range of compositions.Additionally, a pure ZrO2-SiO2 binary with 1:1 molar ratio was prepared for comparative purposes. The molar concentrations of the different precursors and the respective sample codes are reported in Table 1; the same codes will be used throughout the manuscript. The synthetic procedure is briefly explained as follows. Previously prepared Dy(NO3)3 stock solution as detailed in Table 1 was added to the ZrOCl2 solution under vigorous stirring. The required amount of ethanol was added to this continuously stirred mixture at an operating temperature of 80 °C for 30 minutes. This was followed by the addition of 1 M TEOS to the solution under constant stirring conditions and finally 0.1 M of HNO3 was added to this mixture as a catalyst. The homogeneous solut...

Structural, optical tuning, and mechanical behavior of zirconia toughened alumina through europium substitutions

“…, However, EZTA20 that indicated the only presence of c ‐ZrO 2 through XRD analysis still indicated the existence of t ‐ZrO 2 trace contributed from the less intense bands detected at 144 and 267 cm −1 . Along with t ‐ZrO 2 trace, EZTA20 also displayed the incidence of strong c ‐ZrO 2 Raman active mode at 620 cm ‐1 Thus, the persistence of t ‐ZrO 2 trace signified a partial t ‐ → c ‐ZrO 2 transition in EZTA20.…”

Structural, Mechanical, Imaging and in Vitro Evaluation of the Combined Effect of Gd3+ and Dy3+ in the ZrO2–SiO2 Binary System

“…(CZS) and Dy 3+ (DZS) additions in ZrO2-SiO2 binary systems. [10][11][12][13] The considerable size difference between La 3+ (1.06 Å) and Zr 4+ (0.79 Å) restricts the entry of La 3+ into the ZrO2 lattice and as a consequence the quantitative analysis implies negligible changes in the lattice data of t-ZrO2 in LZS systems. The smaller ionic size of Ce 4+ (0.97 Å) than La 3+ permits the entry of Ce 4+…”

“…The 148, 268, 320, 465, 650 cm -1 bands pertaining to t-ZrO2 28 are clearly observed for GDZS-5 and at a slightly reduced intensity for GDZS-10, however with GDZS-20 the bands are only slightly more intense than the background. The bands characteristic of c-ZrO2 are at 618, 305 and 140 cm -1 13,29. For GDZS-30 only the band at 618 cm -1 is evident and shifted towards a lower wave number.…”

“…(CZS) to the ZrO2-SiO2 system have been reported. [10][11][12][13] La 3+ additions stabilizes the t-ZrO2…”

“…15 The contrast nature of Dy 3+ doped ZrO2-SiO2 system has been previously reported by the authors. 13 Furthermore, the high atomic number and K-edge energy values of Z = 66 and 53.8 keV respective of Dy 3+ ensures a high X-ray attenuation coefficient of 3.36 cm 2 .g -1 at 100 keV and hence it is also employed as a X-Ray computed tomography (CT) contrast agent. 16 Thus this study explores the simultaneous additions of Gd 3+ and Dy 3+ to the ZrO2-SiO2 system followed by a systematic characterisation of the structural behaviour, resulting mechanical properties and multi-modal imaging features.…”