Abstract

An uncommon phase transformation on 5 mol %YNbO4-modified Zirconia (3Y) in the isothermal sintering condition within a range of 1300-1500°C for 1 to 11 hours of dwell time that suffered from mechanical surface grinding treatment was investigated. Fabrication methods that used were oxide mixing (OM) and polymeric combustion method (CM), and the samples were denoted by O and C, respectively. Phase transformation behavior was investigated using X-ray diffraction, Raman spectra and Wire peaks simulations software, respectively. SEM/EDS were carried out to investigate microstructural characteristics and elemental distribution, and also Vickers microindentation was applied to measure the fracture toughness value.
Fracture toughness of 1300°C for 1 hour sintered O specimen (O13x1) which was sintered under the lowest heat treatment temperature achieved 9.39 MPa√m, while for the higher heat treatment temperature specimen, 1500°C for 5 hours (O15x5), achieved 18.77 MPa√m. The increasing of heat treatment temperature is followed by the increasing of fracture toughness for the specimens without over heat treatment.
The toughening mechanism may be related to composition changed due to applied stress such as-ground surface mechanical treatment that given to t-, c-, and tetragonal prime (t’-) phase which also exist in this system. The composition of c- and t’-phase of 1500°C for 1 hour sintered (O15x1) specimen is 27% and 3%, respectively, due to surface treatment the composition changed to 25% and 7%, respectively. The composition changed behavior reflects the existence of transformability in c-phase. Phase transformation is also traced by Raman spectra investigation. The higher frequencies of the Raman modes for c- and t- phases were decrease as increasing of dwell time that correlate to a-axis of the crystal structure. It is found that the frequency of tetragonal modes of as-ground specimen comparing to as-sintered one decrease towards lower wavenumber, however, vice versa for the cubic modes.
It can be assumed that lattice change as the result of external applied stress in cubic is not similar to tetragonal. Therefore, the transformability of c-phase is related to the energy absorption and release behavior in materials. The evidence of stress induced c- to t’-phase transformation under applied surface grinding treatment may contributes to the toughening mechanism in zirconia ceramic.
In addition, the present study offers a new simple technique to fabricate homogeneous nanoscale powders (CM). It is found that the t-phase in CM specimen is stable up to 9 hours of dwell time at 1500°C (C15x9), before it transforms to m-phase at fruther heat treatment compare with ordinary fabrication method (OM) which only stable up to 5 hours at 1500°C (O15x5). Accordingly, 1.3 μm is a critical grain size for this system, it is found that both O15x5 and C15x9 have similar grain size around this value, which is confirmed by X-ray diffraction and Raman spectra that t- to m- phase transformation was exhibited. Therefore, the fracture toughness value of 7 and 9 hours of dwell time at 1500°C of C specimens are much higher than those of O specimens at the same heat treatment. This phenomena is also related to homogeneity of CM powders where Yttria element segregation in C specimens is slower than O.

Abstract

An uncommon phase transformation on 5 mol %YNbO4-modified Zirconia (3Y) in the isothermal sintering condition within a range of 1300-1500°C for 1 to 11 hours of dwell time that suffered from mechanical surface grinding treatment was investigated. Fabrication methods that used were oxide mixing (OM) and polymeric combustion method (CM), and the samples were denoted by O and C, respectively. Phase transformation behavior was investigated using X-ray diffraction, Raman spectra and Wire peaks simulations software, respectively. SEM/EDS were carried out to investigate microstructural characteristics and elemental distribution, and also Vickers microindentation was applied to measure the fracture toughness value.
Fracture toughness of 1300°C for 1 hour sintered O specimen (O13x1) which was sintered under the lowest heat treatment temperature achieved 9.39 MPa√m, while for the higher heat treatment temperature specimen, 1500°C for 5 hours (O15x5), achieved 18.77 MPa√m. The increasing of heat treatment temperature is followed by the increasing of fracture toughness for the specimens without over heat treatment.
The toughening mechanism may be related to composition changed due to applied stress such as-ground surface mechanical treatment that given to t-, c-, and tetragonal prime (t’-) phase which also exist in this system. The composition of c- and t’-phase of 1500°C for 1 hour sintered (O15x1) specimen is 27% and 3%, respectively, due to surface treatment the composition changed to 25% and 7%, respectively. The composition changed behavior reflects the existence of transformability in c-phase. Phase transformation is also traced by Raman spectra investigation. The higher frequencies of the Raman modes for c- and t- phases were decrease as increasing of dwell time that correlate to a-axis of the crystal structure. It is found that the frequency of tetragonal modes of as-ground specimen comparing to as-sintered one decrease towards lower wavenumber, however, vice versa for the cubic modes.
It can be assumed that lattice change as the result of external applied stress in cubic is not similar to tetragonal. Therefore, the transformability of c-phase is related to the energy absorption and release behavior in materials. The evidence of stress induced c- to t’-phase transformation under applied surface grinding treatment may contributes to the toughening mechanism in zirconia ceramic.
In addition, the present study offers a new simple technique to fabricate homogeneous nanoscale powders (CM). It is found that the t-phase in CM specimen is stable up to 9 hours of dwell time at 1500°C (C15x9), before it transforms to m-phase at fruther heat treatment compare with ordinary fabrication method (OM) which only stable up to 5 hours at 1500°C (O15x5). Accordingly, 1.3 μm is a critical grain size for this system, it is found that both O15x5 and C15x9 have similar grain size around this value, which is confirmed by X-ray diffraction and Raman spectra that t- to m- phase transformation was exhibited. Therefore, the fracture toughness value of 7 and 9 hours of dwell time at 1500°C of C specimens are much higher than those of O specimens at the same heat treatment. This phenomena is also related to homogeneity of CM powders where Yttria element segregation in C specimens is slower than O.

References

[1] R.W S. Toughening mechanisms for ceramic materials. Journal of the European Ceramic Society 1992;10:131.
[2] Virkar AV, Matsumoto RLK. Ferroelastic Domain Switching as a Toughening Mechanism in Tetragonal Zirconia. Journal of the American Ceramic Society 1986;69:C.
[3] Yuh S-D, Lai Y-C, Chou C-C, Lee H-Y. YNbO4-addition on the fracture toughness of ZrO2(3Y) ceramics. Journal of Materials Science 2001;36:2303.
[4] Yeh T-H, Chou C-C, Lee H-Y. Compression-induced reversible phase transformation with a cubic-like structure in 3mol.% yttria-stabilized zirconia. Scripta Materialia 2009;61:927.
[5] Exner GPaHE. Particle rearrangement in solid state sintering. Metallkd. 1976;67:611.
[6] Rahaman MN. Sintering technology. New York: Marcel Dekker, 1990.
[7] Kang SJL. Sintering: densification, grain growth, and microstructure: Elsevier Butterworth-Heinemann, 2005.
[8] Rahaman MN. Sintering of ceramics: CRC Press, 2007.
[9] S.Manisha Vidyavathy VK. Microwave Sintering of Niobium Co-doped Yttria Stabilized Zirconia. Modern Applied Science 2009;3.
[10] Lee DY, Kim D-J, Kim B-Y. Influence of alumina particle size on fracture toughness of (Y,Nb)-TZP/Al2O3 composites. Journal of the European Ceramic Society 2002;22:2173.
[11] Yoshimura M. Phase stability of zirconia: Ceram. Bull, 1988.
[12] Ho S. On the structural chemistry of zirconium oxide. Materials Science and Engineering 1982;54:23.
[13] Paxton MWFaAT. Crystal structures of zirconia from first principles and self-constant tight binding: Phys. Rev. Lett, 1998.
[14] Stevens R. Zirconia and zirconia ceramics: Magnesium Elektron Ltd, 1986.
[15] Colomer MT, Jurado JR. Structure, Microstructure, and Mixed Conduction of [(ZrO2)0.92(Y2O3)0.08]0.9(TiO2)0.1. Journal of Solid State Chemistry 2002;165:79.
[16] R. Ruh KSM, P.G. Valentine, and H.O. Bielstein. Phase relations in the system ZrO2-Y2O3 at low Y2O3 contents. J. Am. Ceram. Soc 1984;67:C190.
[17] Reed JS, Lejus A-M. Affect of grinding and grinding on near-surface phase transformations in zirconia. Materials Research Bulletin 1977;12:949.
[18] Skovgaard M, Ahniyaz A, Sørensen BF, Almdal K, van Lelieveld A. Effect of microscale shear stresses on the martensitic phase transformation of nanocrystalline tetragonal zirconia powders. Journal of the European Ceramic Society 2010;30:2749.
[19] Toraya H, Yoshimura M, Somiya S. Calibration Curve for Quantitative Analysis of the Monoclinic-Tetragonal ZrO2 System by X-Ray Diffraction. Journal of the American Ceramic Society 1984;67:C.
[20] Paterson AW, Stevens R. Preferred orientation of the transformed monoclinic phase in fracture surfaces of Y-TZP ceramics. International Journal of High Technology Ceramics 1986;2:135.
[21] Zhu WZ, Lei TC, Zhou Y, Ding ZS. Ageing behaviour of t′-phase in a hot-pressed ZrO2(4 mol% Y2O3) ceramic. Journal of Materials Science 1995;30:6235.
[22] Cheng Y, Thompson DP. The transformability of tetragonal ZrO₂ in some glass systems. Journal of Materials Science Letters 1990;9:24.
[23] Casellas D, Feder A, Llanes L, Anglada M. Fracture toughness and mechanical strength of Y-TZP/PSZ ceramics. Scripta Materialia 2001;45:213.
[24] Bravo-Leon A, Morikawa Y, Kawahara M, Mayo MJ. Fracture toughness of nanocrystalline tetragonal zirconia with low yttria content. Acta Materialia 2002;50:4555.
[25] Lange FF. Transformation-Toughened ZrO2: Correlations between Grain Size Control and Composition in the System ZrO2-Y2O3. Journal of the American Ceramic Society 1986;69:240.
[26] Trunec M, Chlup Z. Higher fracture toughness of tetragonal zirconia ceramics through nanocrystalline structure. Scripta Materialia 2009;61:56.
[27] Mazaheri M, Simchi A, Golestani-Fard F. Densification and grain growth of nanocrystalline 3Y-TZP during two-step sintering. Journal of the European Ceramic Society 2008;28:2933.
[28] Kim D-J, Jung H-J, Cho D-H. Phase transformations of Y2O3 and Nb2O5 doped tetragonal zirconia during low temperature aging in air. Solid State Ionics 1995;80:67.
[29] Kim D-J, Jung H-J, Jang J-W, Lee H-L. Fracture Toughness, Ionic Conductivity, and Low-Temperature Phase Stability of Tetragonal Zirconia Codoped with Yttria and Niobium Oxide. Journal of the American Ceramic Society 1998;81:2309.
[30] Kim D-J, Jang J-W, Lee H-L. Effect of Tetravalent Dopants on Raman Spectra of Tetragonal Zirconia. Journal of the American Ceramic Society 1997;80:1453.
[31] Shi JL, Li BS, Lu ZL, Huang XX. Correlation between microstructure, phase transformation during fracture and the mechanical properties of Y-TZP ceramics. Journal of the European Ceramic Society 1996;16:795.
[32] Coble RL. Sintering Crystalline Solids. II. Experimental Test of Diffusion Models in Powder Compacts. Journal of Applied Physics 1961;32:793.
[33] Deshmane VG, Adewuyi YG. Synthesis of thermally stable, high surface area, nanocrystalline mesoporous tetragonal zirconium dioxide (ZrO2): Effects of different process parameters. Microporous and Mesoporous Materials 2012;148:88.
[34] A T. The intercept method—2. Determination of spatial grain size. Acta Materialia 1997;45:595.
[35] Fisher JC, Fullman RL, Sears GW. On the origin of screw dislocations in growing crystals. Acta Metallurgica 1954;2:344.
[36] Chou C-S, Yang R-Y, Chen J-H, Chou S-W. The optimum conditions for preparing the lead-free piezoelectric ceramic of Bi0.5Na0.5TiO3 using the Taguchi method. Powder Technology 2010;199:264.
[37] Mendelson MI. Average Grain Size in Polycrystalline Ceramics. Journal of the American Ceramic Society 1969;52:443.
[38] Borrell A, Salvador MD, Rayón E, Peñaranda-Foix FL. Improvement of microstructural properties of 3Y-TZP materials by conventional and non-conventional sintering techniques. Ceramics International 2012;38:39.
[39] Casellas D, Cumbrera FL, Sánchez-Bajo F, Forsling W, Llanes L, Anglada M. On the transformation toughening of Y–ZrO2 ceramics with mixed Y–TZP/PSZ microstructures. Journal of the European Ceramic Society 2001;21:765.
[40] Yeh T-H, Chou C-C. Doping effect and vacancy formation on ionic conductivity of zirconia ceramics. Journal of Physics and Chemistry of Solids;69:386.
[41] Motohashi Y, Sekigami T, Sugeno N. Variation in some mechanical properties of Y-TZP caused by superplastic compressive deformation. Journal of Materials Processing Technology 1997;68:229.
[42] Sakuma T, Yoshizawa Y-I, Suto H. The microstructure and mechanical properties of yttria-stabilized zirconia prepared by arc-melting. Journal of Materials Science 1985;20:2399.
[43] Luthardt RG, Holzhüter M, Sandkuhl O, Herold V, Schnapp JD, Kuhlisch E, Walter M. Reliability and Properties of Grind Y-TZP-Zirconia Ceramics. Journal of Dental Research 2002;81:487.
[44] R.Ahmad BMW, S.M.Morgano. Grinding mechanism and its effect on the mechanical properties of ceramic restorations - a review of the literature. Annals of Dentistry 2001.
[45] Işerı U, Ozkurt Z, Kazazoğlu E, uuml, ccedil, koğlu D. Influence of grinding procedures on the flexural strength of zirconia ceramics, 2010.
[46] Kuo C-W, Shen Y-H, Wen S-B, Lee H-E, Hung IM, Huang H-H, Wang M-C. Phase transformation kinetics of 3 mol% yttria partially stabilized zirconia (3Y-PSZ) nanopowders prepared by a non-isothermal process. Ceramics International 2011;37:341.
[47] Ray JC, Pati RK, Pramanik P. Chemical synthesis and structural characterization of nanocrystalline powders of pure zirconia and yttria stabilized zirconia (YSZ). Journal of the European Ceramic Society 2000;20:1289.
[48] Chunsheng Y, Qisheng W, Yuanyuan L. Stabilized Y-Ce-ZrO2 Nano-Powder Prepared by Alcohol-Aqueous Heating and Hydrothermal Synthesis. Journal of Rare Earths 2007;25, Supplement 2:250.
[49] Guo GY, Chen YL. Unusual structural phase transition in nanocrystalline zirconia. Applied Physics A: Materials Science & Processing 2006;84:431.
[50] Štefanić G, Musić S, Gržeta B, Popović S, Sekulić A. Influence of pH on the stability of low temperature t-ZrO2. Journal of Physics and Chemistry of Solids;59:879.
[51] Djuričić B, Pickering S, McGarry D, Glaude P, Tambuyser P, Schuster K. The properties of zirconia powders produced by homogeneous precipitation. Ceramics International 1995;21:195.
[52] Hasegawa H, Hioki T, Kamigaito O. Cubic-to-rhombohedral phase transformation in zirconia by ion implantation. Journal of Materials Science Letters 1985;4:1092.
[53] Sakuma T, Yoshizawa Y-I, Suto H. The rhombohedral phase produced in partially-stabilized zirconia. Journal of Materials Science Letters 1985;4:29.
[54] Kitano Y, Mori Y, Ishitani A, Masaki T. Rhombohedral Phase in Y2O3-Partially-Stabilized ZrO2. Journal of the American Ceramic Society 1988;71:C.
[55] Nomura K, Mizutani Y, Kawai M, Nakamura Y, Yamamoto O. Aging and Raman scattering study of scandia and yttria doped zirconia. Solid State Ionics 2000;132:235.
[56] Wulfman C, Sadoun M, Lamy de la Chapelle M. Interest of Raman spectroscopy for the study of dental material: The zirconia material example. IRBM;31:257.
[57] Sekulić A, Furić K, Stubičar M. Raman study of phase transitions in pure and alloyed zirconia induced by ball-milling and a laser beam. Journal of Molecular Structure 1997;410-411:275.
[58] Ghosh A, Suri AK, Pandey M, Thomas S, Rama Mohan TR, Rao BT. Nanocrystalline zirconia-yttria system–a Raman study. Materials Letters 2006;60:1170.
[59] Liang B, Ding C, Liao H, Coddet C. Study on structural evolution of nanostructured 3 mol% yttria stabilized zirconia coatings during low temperature ageing. Journal of the European Ceramic Society 2009;29:2267.
[60] Gibson IR, Irvine JTS. Qualitative X-ray Diffraction Analysis of Metastable Tetragonal (t′) Zirconia. Journal of the American Ceramic Society 2001;84:615.
[61] Baither D, Baufeld B, Messerschmidt U, Foitzik AH, Rühle M. Ferroelasticity of t‘-Zirconia: I, High-Voltage Electron Microscopy Studies of the Microstructure in Polydomain Tetragonal Zirconia. Journal of the American Ceramic Society 1997;80:1691.
[62] Baufeld B, Baither D, Messerschmidt U, Bartsch M, Foitzik AH, Rühle M. Ferroelasticity of t‘-Zirconia: II, In situ Straining in a High-Voltage Electron Microscope. Journal of the American Ceramic Society 1997;80:1699.
[63] Khor KA, Yang J. Transformability of t-ZrO2 and lattice parameters in plasma sprayed rare-earth oxides stabilized zirconia coatings. Scripta Materialia 1997;37:1279.
[64] Khor KA, Yang J. Lattice parameters, tetragonality (ca) and transformability of tetragonal zirconia phase in plasma-sprayed ZrO2-Er2O3 coatings. Materials Letters 1997;31:23.
[65] Budiansky B, Truskinovsky L. On the mechanics of stress-induced phase transformation in zirconia. Journal of the Mechanics and Physics of Solids 1993;41:1445.
[66] Lee H-E, Du J-K, Sie Y-Y, Wang C-H, Wu J-H, Wang C-L, Hwang WS, Huang H-H, Li W-L, Wang M-C. Thermal Properties and Phase Transformation of 2 mol% Y2O3-PSZ Nanopowders Prepared by a Co-precipitation Process. Journal of Non-Crystalline Solids 2011;357:2103.
[67] Hsu Y-W, Yang K-H, Chang K-M, Yeh S-W, Wang M-C. Synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanosized powders prepared using a simple co-precipitation process. Journal of Alloys and Compounds 2011;509:6864.
[68] Lei L, Fu Z, Wang H, Lee SW, Niihara K. Transparent yttria stabilized zirconia from glycine-nitrate process by spark plasma sintering. Ceramics International 2012;38:23.
[69] Dahl P, Kaus I, Zhao Z, Johnsson M, Nygren M, Wiik K, Grande T, Einarsrud MA. Densification and properties of zirconia prepared by three different sintering techniques. Ceramics International 2007;33:1603.
[70] Tahmasebpour M, Babaluo AA, Aghjeh MKR. Synthesis of zirconia nanopowders from various zirconium salts via polyacrylamide gel method. Journal of the European Ceramic Society 2008;28:773.
[71] Patil DS, Prabhakaran K, Durgaprasad C, Gokhale NM, Samui AB, Sharma SC. Synthesis of nanocrystalline 8 mol% yttria stabilized zirconia by the oleate complex route. Ceramics International 2009;35:515.
[72] Garvie RC, Goss MF. Intrinsic size dependence of the phase transformation temperature in zirconia microcrystals. Journal of Materials Science 1986;21:1253.
[73] Djurado E, Bouvier P, Lucazeau G. Crystallite Size Effect on the Tetragonal-Monoclinic Transition of Undoped Nanocrystalline Zirconia Studied by XRD and Raman Spectrometry. Journal of Solid State Chemistry 2000;149:399.
[74] Chraska T, King AH, Berndt CC. On the size-dependent phase transformation in nanoparticulate zirconia. Materials Science and Engineering: A 2000;286:169.
[75] Li M, Feng Z, Xiong G, Ying P, Xin Q, Li C. Phase Transformation in the Surface Region of Zirconia Detected by UV Raman Spectroscopy. The Journal of Physical Chemistry B 2001;105:8107.