Availableonlineatwww.sciencedirect.com DIRECT. NIM B Beam Interactions with Materials atoms ELSEVIER Nuclear Instruments and Methods in Physics Research B 250(2006)95-100 www.elsevier.com/locate/nimb Phase transition of pure zirconia under irradiation: a textbook example D. Sin G. Baldinozzi.d. gosset a.s. le caer CEAISaclay, DENDMNSRMAILA2M, F-91191 Gif sur Yvette, France b Laboratoire de Structures, Proprietes et Modelisation des Solides, UMR CNRS 8580 Ecole Centrale Paris, F-92295 Chatenay Malabry,france CEA/Saclay, DSMIDRECAMISCMIURA 331 CNRS, F./ Gif sur Yvette, Fran Available online 13 June 2006 Abstract One of the most important goals in ceramic and materials science is to be able to design materials with specific properties. Irradiation seems to be a powerful tool for the design of advanced ceramics because of its ability to modify over different scales the microstructure of solids. Nowadays, it is clearly proved that irradiation induces order-disorder phase transitions in metallic alloys and in some ceramics. In this paper, we show that a displacive phase transition can also be induced by irradiation. Based on many experimental facts, a micro- scopic model is proposed to explain the displacive phase transition observed in this material after irradiation. Defects, produced in the oxygen sublattice, induce important strain fields on a nanometric scale. This strain field can be handled as a secondary order parameter within the Landau theory approach, leading to a decrease of the phase transition temperature and thus quenching the high temperature tetragonal phase c 2006 Elsevier B.V. all rights reserved PACS:6180.Jh;64.70.Kb Keywords: Irradiation effect; Phase transition; Point defects 1. Introduction has then been the object of extensive investigations, and therefore it is a textbook example for describing the displa At high temperature, most solids are in a thermody- cive phase transition out of irradiation within the Landau namic equilibrium state. At low temperature this is not theory approach [8]. Under irradiation, it is quite surpris- always true since their relaxation timescales can be very ing that displacive transitions associated to correlated long. Therefore, a perturbation of the system will not movements of atoms can occur. In fact, displacement cas- always allow the system to reach the equilibrium ground cades and amorphous tracks, breaking the spatial coher state [1]. Sometimes, the system perturbation is so impor- ence of the crystal, should forbid such a mechanism tant that the phase transition sequence can be modified: Nevertheless, some authors [9] attemped to explain amor several examples, like the occurrence of order-disorder phisation of some oxides within the Landau theory frame- phase transitions driven by irradiation in metallic alloys, work. In this paper, the analysis of different experiments are discussed by many authors [2, 3]. A phase transition done on pure monoclinic zirconia out of and under irradi induced by irradiation has also been observed in zirconia ation allows us to build a simple microscopic model 4-6 where the monoclinic to tetragonal phase occurs. explaining the monoclinic to tetragonal phase transition Some authors [7] have also observed the effect of grain size observed in pure zirconia samples. To reach such a goal on radiation induced transformations in zirconia. Zirconia we have studied the phase transition triggered by the temperature in this solid The key parameters associated with this transition were described within the landau Corresponding author. Tel: +331 69 08 29 20 fax: +33 1 69 08 90 82. framework of phase transitions. On the other hand, to E-mail address: david simeone(@cea. fr(D. Simeone) understand the impact of different order parameters in this 0168-583XS. see front matter c 2006 Elsevier B v. All rights doi:l0.l016 i nimb200604.092Phase transition of pure zirconia under irradiation: A textbook example D. Simeone a,*, G. Baldinozzi b , D. Gosset a , S. Le Cae¨r c a CEA/Saclay, DEN/DMN/SRMA/LA2M, F-91191 Gif sur Yvette, France b Laboratoire de Structures, Proprie´te´s et Mode´lisation des Solides, UMR CNRS 8580 Ecole Centrale Paris, F-92295 Chaˆtenay Malabry, France c CEA/Saclay, DSM/DRECAM/SCM/URA 331 CNRS, F-91191 Gif sur Yvette, France Available online 13 June 2006 Abstract One of the most important goals in ceramic and materials science is to be able to design materials with specific properties. Irradiation seems to be a powerful tool for the design of advanced ceramics because of its ability to modify over different scales the microstructure of solids. Nowadays, it is clearly proved that irradiation induces order–disorder phase transitions in metallic alloys and in some ceramics. In this paper, we show that a displacive phase transition can also be induced by irradiation. Based on many experimental facts, a micro￾scopic model is proposed to explain the displacive phase transition observed in this material after irradiation. Defects, produced in the oxygen sublattice, induce important strain fields on a nanometric scale. This strain field can be handled as a secondary order parameter within the Landau theory approach, leading to a decrease of the phase transition temperature and thus quenching the high temperature tetragonal phase. 2006 Elsevier B.V. All rights reserved. PACS: 61.80.Jh; 64.70.Kb Keywords: Irradiation effect; Phase transition; Point defects 1. Introduction At high temperature, most solids are in a thermody￾namic equilibrium state. At low temperature this is not always true since their relaxation timescales can be very long. Therefore, a perturbation of the system will not always allow the system to reach the equilibrium ground state [1]. Sometimes, the system perturbation is so impor￾tant that the phase transition sequence can be modified: several examples, like the occurrence of order–disorder phase transitions driven by irradiation in metallic alloys, are discussed by many authors [2,3]. A phase transition induced by irradiation has also been observed in zirconia [4–6] where the monoclinic to tetragonal phase occurs. Some authors [7] have also observed the effect of grain size on radiation induced transformations in zirconia. Zirconia has then been the object of extensive investigations, and therefore it is a textbook example for describing the displa￾cive phase transition out of irradiation within the Landau theory approach [8]. Under irradiation, it is quite surpris￾ing that displacive transitions associated to correlated movements of atoms can occur. In fact, displacement cas￾cades and amorphous tracks, breaking the spatial coher￾ence of the crystal, should forbid such a mechanism. Nevertheless, some authors [9] attemped to explain amor￾phisation of some oxides within the Landau theory frame￾work. In this paper, the analysis of different experiments done on pure monoclinic zirconia out of and under irradi￾ation allows us to build a simple microscopic model explaining the monoclinic to tetragonal phase transition observed in pure zirconia samples. To reach such a goal, we have studied the phase transition triggered by the temperature in this solid. The key parameters associated with this transition were described within the Landau framework of phase transitions. On the other hand, to understand the impact of different order parameters in this 0168-583X/$ - see front matter 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.04.092 * Corresponding author. Tel.: +33 1 69 08 29 20; fax: +33 1 69 08 90 82. E-mail address: david.simeone@cea.fr (D. Simeone). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 250 (2006) 95–100 NIMB Beam Interactions with Materials & Atoms