Zirconium oxide and the crystallinity hallows
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RESEARCH
Zirconium oxide and the crystallinity hallows Roberto Nisticò 1 Received: 7 February 2020 / Revised: 18 September 2020 / Accepted: 16 October 2020 # Australian Ceramic Society 2020
Abstract Zirconium oxide is one of the most promising ceramic materials as it finds applications in several high-level technological fields, ranging from biomedicine to sensing. Zirconium oxide is characterized by showing very uncommon properties for being a ceramic substrate, such as a certain plastic behavior once subjected to mechanical stress, a naturally occurring phase transformation toughening, as well as a dramatic sensibility toward water-induced aging (if hydrothermally treated). In general, all these properties are strictly correlated with the tetragonal-to-monoclinic interphase transformation and, consequently, driven by the stabilization of the tetragonal phase. Hence, in this study, a summary of the main relevant principles guiding zirconium oxide interphase transformations is proposed, highlighting the important role of stabilizers and the correlation between microstructure and doping. A particular emphasis has been dedicated to the thermodynamics behind these phenomena. Keywords Aging . Ceramic materials . Doping . Microstructures . Phase transformation toughening . Zirconia
Introduction The comprehension of the physicochemical and mechanical properties of ceramic oxides has significantly grown over the past years, thus making this highly varied class of materials being employed not only in the more traditional uses (i.e., either structural or insulating materials), but also in biomedicine, energy storage, aerospace and automotive, water filtering and remediation, surface coatings technology, sensing and dosing, nanotechnology, and (photo)catalysis [1–10]. Among the different ceramics, zirconium oxide (ZrO2), or zirconia, is one of the most studied and industrially applied metal oxides. This ceramic was formerly discovered in 1789 by the German chemist Martin H. Klaproth as a reaction product at the end of the thermal process of zirconium silicate gems (or zircon) [11]. However, it should be reminded that zirconia occurs also as a natural mineral, under the name of “baddeleyte” (in honor of Joseph Baddeley). Initially found in Rakwana (Sri Lanka) in 1892 [12], such native mineral contains 80–90% of zirconium oxide (ZrO2), with major impurities of Ti, Hf, Y, Fe, Nb, and Si [13]. Due to the presence of such heteroatoms in the
* Roberto Nisticò
1
Via Borgomasino 39, 10149 Torino, Italy
past, zirconia has been used blended with these rare earth oxides as a pigment in other ceramic materials [14]. Furthermore, in the recent period, zirconia has been extensively exploited mostly in gas sensing (i.e., the lambda sensor applied for the detection of oxygen) and in biomedicine (as dental prosthesis) [14–17]. Due to its biological inertness [18], zirconia was initially exploited also in hip and knee replacement until the Prozyr® failure event in 2001 (well-described by Chevalier in [19]), which opened to a controvers
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