A.A. Sobol, Y.K. Voronko Journal of Physics and Chemistry of Solids 65 (2004)1103-1112 1105 Load domains results in the appearance of only lines of the 3E modes in the Raman spectrum for the 1 geometry (D, F column in Table 2). Thus, registration of polarized Raman spectra is the reliable method of revealing results of the stress- [001] induced C-I transformation under loading However, at first sight, it is impossible to carry out above-mentioned experiments. Bulk tetragonal single crystals of own. as to crystals of Y-PSZ synthesized by cold container technique, they appear as milky color due to the presence of large dimension tetragonal precipitates and are inadequate for the [010] polarized Raman spectroscopy studies The application of the polarized Raman spectroscopy for studying the C-t transformation in PSZ single crystals is possible due to the specific mechanism of tetragonal phase formation in ZrO2-Gd2O3(Eu2O3)(6-8 mol%)[17, 22) solid solutions. which will be described belot [100] Ea 4. Formation of the tetragonal phase in ZrOz-Gd2O3 (Eu2O3)solid solutions Fig. 2. Orientation of the isolated tetragonal domains B, D and F in the volume of ZrO2-Gd2 O3(Eu,O3)( 8 mol%)cubic solid solution. En and E, are the directions of Eex-electric vector of the excitation A nature of t-domain formation can be qualitatively explained for ZrO2-rich region of the equilibrium ZrO2 Gd2O3(Eu2O3) phase diagram(Fig 3). The diagram of the Deformation along the definite CA axis in the process of description of the systems under study. The temperature T1 C-d transformation created the different conditions for separates the cubic and the cubic +tetragonal (C+t) nucleation of B, D and F types of t' domains(Fig. 2) regions, whereas To denotes the temperature of the C-t Loading can induce the predominant formation of either b phase transformation. These temperatures were determined or D+ Domain. The predominant formation of the B domain to be in the region of 1400-1700 K for ZrO2-Gd2O3 would result in decreasing the intensity of the Alg mode in the (Eu2O3)(6-8 mol%)samples [17]. There was an essential conditions of the gec omer difference in the phase formation at different annealin component of the Alg Raman tensor from the summarized temperatures(points 2 and 3 in Fig 3). The temperature of intensity equation of the 2B, D, F column (Table 2). More- the point 2 lies between T1 and To. The usual decomposition over,only lines of the 2B,g modes should be registered in the of the C-solid solution due to diffusion-controlled reaction spectrum of the 1 geometry at the predominant B domain must occur at this temperature [22]. Decomposition formation. In contrast, the predominant formation of D+F products are the low-Gd2O3(Eu2O3) t-phase(=2.5 mol% Table 2 Calculated intensities of the tetragonal vibrational modes in the parallel (ID)and the crossed( l )scattering geometries for three types of domains according to Fg.2(Eax‖E1) The domain SD.F E(1) 000 EDeformation along the definite C4 axis in the process of C ! t 0 transformation created the different conditions for nucleation of B; D and F types of t0 domains (Fig. 2). Loading can induce the predominant formation of either B orD þ F domain. The predominant formation of theB domain would result in decreasing the intensity of the A1g mode in the conditions of the k geometry due to canceling the azz component of the A1g Raman tensor from the summarized intensity equation of the PB; D; F column (Table 2). More￾over, only lines of the 2B1g modes should be registered in the spectrum of the ’ geometry at the predominant B domain formation. In contrast, the predominant formation of D þ F domains results in the appearance of only lines of the 3Eg modes in the Raman spectrum for the ’ geometry (PD; F column in Table 2). Thus, registration of polarized Raman spectra is the reliable method of revealing results of the stress￾induced C ! t 0 transformation under loading. However, at first sight, it is impossible to carry out the above-mentioned experiments. Bulk tetragonal single crystals of a pure ZrO2 cannot be grown. As to single crystals of Y–PSZ synthesized by cold container technique, they appear as milky color due to the presence of large￾dimension tetragonal precipitates and are inadequate for the polarized Raman spectroscopy studies. The application of the polarized Raman spectroscopy for studying the C ! t 0 transformation in PSZ single crystals is possible due to the specific mechanism of tetragonal phase formation in ZrO2 –Gd2O3 (Eu2O3) (6–8 mol%) [17,22] solid solutions, which will be described below. 4. Formation of the tetragonal phase in ZrO2 –Gd2O3 (Eu2O3) solid solutions A nature of t0 -domain formation can be qualitatively explained for ZrO2-rich region of the equilibrium ZrO2 – Gd2O3 (Eu2O3) phase diagram (Fig. 3). The diagram of the ZrO2 –Y2O3 system [23] was used as a prototype for the description of the systems under study. The temperature T1 separates the cubic and the cubic þ tetragonal (C þ t) regions, whereas T0 denotes the temperature of the C ! t 0 phase transformation. These temperatures were determined to be in the region of 1400–1700 K for ZrO2 –Gd2O3 (Eu2O3) (6–8 mol%) samples [17]. There was an essential difference in the phase formation at different annealing temperatures (points 2 and 3 in Fig. 3). The temperature of the point 2 lies between T1 and T0: The usual decomposition of the C-solid solution due to diffusion-controlled reaction must occur at this temperature [22]. Decomposition products are the low-Gd2O3 (Eu2O3) t-phase (<2.5 mol% Fig. 2. Orientation of the isolated tetragonal domains B; D and F in the volume of ZrO2 –Gd2O3 (Eu2O3) (8 mol%) cubic solid solution. E1 and E2 are the directions of Eex-electric vector of the excitation beam. Table 2 Calculated intensities of the tetragonal vibrational modes in the parallel (k) and the crossed ( ’ ) scattering geometries for three types of domains according to Fig. 2 (EexkE1) The mode The domain BDF PB; D; F PD; F k ’ k ’ k ’ k ’ k ’ A1g a 2 0 a 2 0 b 2 0 2a 2 þ b 2 0 a 2 þ b 2 0 B1g 0 c 2 00 00 0 c 2 0 0 Eg 00 0 e 2 0 e 2 0 2e 2 0 2e 2 A1g ¼ a 0 0 0 a 0 0 0 b ; B1g ¼ c 0 0 0 2c 0 000 ; Egð1Þ ¼ 000 0 0 e 0 e 0 ; Egð2Þ ¼ 0 0 2e 000 2e 0 0 A.A. Sobol, Y.K. Voronko / Journal of Physics and Chemistry of Solids 65 (2004) 1103–1112 1105