Terahertz probing of low‐temperature degradation in zirconia bioceramics

Abstract

ZrO2‐based ceramics are widely used in biomedical applications due to its color, biocompatibility, and excellent mechanical properties. However, low‐temperature degradation (LTD) introduces a potential risk for long‐term reliability of these materials. The development of innovative nondestructive techniques, which can explore LTD in zirconia‐derived compounds, is strongly required. Yttria stabilized zirconia, 3Y‐TZP, is one of the well‐developed ZrO2‐based ceramics with improved resistance to LTD for dental crown and implant applications. Here, 3Y‐TZP ceramic powders were pressed and sintered to study the LTD phenomenon by phase transition behavior. The LTD‐driven tetragonal‐to‐monoclinic phase transition was confirmed by XRD. XPS analysis demonstrated that induced LTD reduced the oxygen vacancies which supports these findings. It is proved that after the degradation, the 3Y‐TZP ceramics show the decreased dielectric permittivity at terahertz frequencies due to the crystallographic phase transformation. Terahertz nondestructive probe is a promising method to investigate LTD in zirconia ceramics.

Temperature dependence in ageing process in commercial zirconia dental ceramics

“…Mechanical properties were measured with corresponding results shown in Table 2 for samples S1, S2, S3, and S4. The samples S1, S2, and S3 are stable with no major deviation from the hardness and fracture toughness values compared to the literature [9,11,[29][30][31]. However, S4 has reduced hardness and K ic values which results from t-phase to m-phase transformation caused by LTD due to a higher LTD temperature of 134°C compared to 100°C for other samples.…”

“…However, there are still some factors that fail the material over time, currently, the most investigated and discussed reason for failure of zirconia-based materials is ageing, which is also called as low-temperature degradation (LTD) [3,8,9]. The LTD is the process in which material transform from tetragonal phase (t-phase) to monoclinic phase (m-phase) spontaneously in the wet environment at low temperature [9][10][11]. This phenomenon restricts its application in dental and other prosthesis [12].…”

“…Herein, m f is m-phase content, m a and ta represent the peak area of monoclinic phase and tetragonal phase, respectively, at given position in the XRD curve [11]. Scanning electron microscopy (SEM) and energy dispersive X-ray EDS data were obtained by using FEI inspect-F (Oxford equipment).…”

Terahertz Characterization of Lead-Free Dielectrics for Different Applications

“…Using Fourier transformation, the detected time domain signals are transformed into the THz time domain, where both amplitude and phase information are acquired, i.e., to achieve broadband and coherent spectroscopy. The complex dielectric properties of materials can then be worked out . The coherent features come from the same femtosecond laser, for example, Ti:Sapphire laser.…”

“…The complex dielectric properties of materials can then be worked out. 12 The coherent features come from the same femtosecond laser, for example, Ti:Sapphire laser. The laser power is split into two paths: one with major power (90% of laser's emission, approximately a few hundreds of milliwatts typically) to generate THz emission and the other for THz detection.…”