A.A. Sobol, Y.K. Voronko / Journal of Physics and Chemistry of Solids 65 (2004)1103-1112 the Eu2O3-content in the series of rapidly quenched melts presented in Fig 4. Finally, the Raman spectrum of the ZrO2 A1(265cm) mol%)quenched melt after the I h low-temperature annealing was practically similar to that of the quenched melt with Eu2O3 (2.5 mol%)(Figs. 4 and 7). Thus, the low- (2) temperature mechanism gives an opportunity to create a large number of t' particles with a variable concentration of Eu20 up to 2.5 mol% in the volume of the primary ZrO2-Eu2O3 (8 mol%)solid solution. The small intensity of the broad band in the region of 600 cm for the Raman spectra of the sample after 1-hour low-temperature annealing(Fig. 7)indicates a retention of only small quantity of the Eu2O3-rich volume in his case. The presence of the Eu2O3-rich phase in the sample 200400600800 subjected by 1-hour low-temperature annealing could be registered also according to the low-intensity A band at A(242cm) (b) 80cm in the Raman spectrum(Fig. 7). This band was shown to be the 'Boson peak'appeared in the Raman spectra of disordered ZrO2-Ln-O3 with the Ln, O3 content above 6 8 mol% 11 Different mechanisms of the tetragonal phase formation in ZrO2-Gd,O3(Eu,O3)(6-8 mol%) solid solutions essentially influence on the transparency of single crystals synthesized by cold-container method. The formation of the large-sized t-particles with 2.5-3 mol% stabilizers due to 2B1g+3Eg ⊥ the diffusion-controlled reaction resulted in the milky single crystals. These crystals stayed nontransparent after anneal 0200400600800 ing at T>T for a long time( several days)[17]. In turn, Raman shift(cm") low-temperature mechanism retained the single crystals totally transparent in spite of the presence of t-domains with Fig.. The polarized Raman spectra at 300 K of the as-grown Zro2 This implies that the size of t'-particles formed in the course EalIE, and elIE, respectively (according to Fi. on ckoi ystals I the same low concentration(2.5-3 mol %)of the stabilizer. (Eu] 03)(8 mol%)(a) and Zr0z-(Gd2O3)(8 mol%)(b) single and 2 are the nc vector of the C-t transformation in ZrO2-Gd2O3(Eu2O3)(6- 8 mol%)crystals was essentially smaller than the wave- (2.5 mol%)t- domains in the as-received ZrO2-Eu2O3 length of visible light. Low-temperature annealing of such (8 mol%) single crystal(Fig. 8a). This implies that the samples did not result in a growth in the dimensions of t'. C-d transformation accompanied by reducing the Eu2O3 nanodomains and only caused decreasing the stabilizer content in t'-domains occurred in the process of Zro2 concentration [17]. Thus, there was a possibility to create Eu2O3 (8 mol%)crystal growth. The spectrum of this crystal oriented nanoparticles of the tetragonal phase with stabilizer co pletely polarized lines(Fig. &a, 1) concentration on the order of 2.5-8 mol% in the volume of when(according to Fig. 2)the electric vector(Ecx) of 6)(6-8 mol%) single crystals. exciting light was parallel to the vector El. By contrast, the Such single crystals were quite suitable for the polarized Raman spectra were completely depolarized(Fig. &a, 2)at Raman spectroscopy studies EexllEy(Fig. 2). This depolarization of exciting and scattered light beams was caused by birefringence phenom enon due to the presence of anisotropic tetragonal domains 6. Polarized Raman spectra of tetragonal phase with the z axes forming the angle of 45 with the eex lle, in nonstressed and stressed PSz single crystals direction(Fig. 2)[12]. Thus, only the EexlIEI geometry could be used for polarized Raman spectroscopy exper Fig. 8 demonstrates the polarized Raman spectra tals. These single crystals were totally transparent due to the one 265-cm line was registered in the ll spectrum,while absence of decomposition processes at such growth the rest five tetragonal modes were observed in the geometry. This is consistent with the calculation results The position of the most intense band at 265 cm and presented in Table 2 for the 2B, D, F column. Thus, the he shape of narrow lines of the Raman spectrum Raman spectra shown in allowed us to reliably demonstrate the predominant existence of Eu2O3 divide the Raman line of the Alg-mode(265 cm )fromthe Eu2O3-content in the series of rapidly quenched melts presented in Fig. 4. Finally, the Raman spectrum of the ZrO2– Eu2O3 (8 mol%) quenched melt after the 1 h low-temperature annealing was practically similar to that of the quenched melt with Eu2O3 (2.5 mol%) (Figs. 4 and 7). Thus, the low￾temperature mechanism gives an opportunity to create a large number of t0 particles with a variable concentration of Eu2O3 up to 2.5 mol% in the volume of the primary ZrO2–Eu2O3 (8 mol%) solid solution. The small intensity of the broad band in the region of 600 cm21 for the Raman spectra of the sample after 1-hour low-temperature annealing (Fig. 7) indicates a retention of only small quantity of the Eu2O3-rich volume in this case. The presence of the Eu2O3-rich phase in the sample subjected by 1-hour low-temperature annealing could be registered also according to the low-intensity A band at 80 cm21 in the Raman spectrum (Fig. 7). This band was shown to be the ‘Boson peak’ appeared in the Raman spectra of disordered ZrO2–Ln2O3 with the Ln2O3 content above 6– 8 mol% [11]. Different mechanisms of the tetragonal phase formation in ZrO2 –Gd2O3 (Eu2O3) (6–8 mol%) solid solutions essentially influence on the transparency of single crystals synthesized by cold-container method. The formation of the large-sized t-particles with 2.5–3 mol% stabilizers due to the diffusion-controlled reaction resulted in the milky single crystals. These crystals stayed nontransparent after anneal￾ing at T . T1 for a long time (several days) [17]. In turn, low-temperature mechanism retained the single crystals totally transparent in spite of the presence of t0 -domains with the same low concentration (2.5–3 mol%) of the stabilizer. This implies that the size of t0 -particles formed in the course of the C ! t 0 transformation in ZrO2 –Gd2O3 (Eu2O3) (6– 8 mol%) crystals was essentially smaller than the wave￾length of visible light. Low-temperature annealing of such samples did not result in a growth in the dimensions of t0 - nanodomains and only caused decreasing the stabilizer concentration [17]. Thus, there was a possibility to create oriented nanoparticles of the tetragonal phase with stabilizer concentration on the order of 2.5–8 mol% in the volume of cubic ZrO2 –Gd2O3 (Eu2O3) (6–8 mol%) single crystals. Such single crystals were quite suitable for the polarized Raman spectroscopy studies. 6. Polarized Raman spectra of tetragonal phases in nonstressed and stressed PSZ single crystals Fig. 8 demonstrates the polarized Raman spectra obtained at 300 K in the case of rapidly grown ZrO2 – Eu2O3 (8 mol%) and ZrO2 –Gd2O3 (8 mol%) single crys￾tals. These single crystals were totally transparent due to the absence of decomposition processes at such growth conditions. The position of the most intense band at 265 cm21 and the shape of narrow lines of the Raman spectrum demonstrate the predominant existence of Eu2O3 (2.5 mol%) t0 -domains in the as-received ZrO2 –Eu2O3 (8 mol%) single crystal (Fig. 8a). This implies that the C ! t 0 transformation accompanied by reducing the Eu2O3 content in t0 -domains occurred in the process of ZrO2 – Eu2O3 (8 mol%) crystal growth. The spectrum of this crystal consisted of narrow completely polarized lines (Fig. 8a, 1) when (according to Fig. 2) the electric vector ðEexÞ of exciting light was parallel to the vector E1: By contrast, the Raman spectra were completely depolarized (Fig. 8a, 2) at EexkE2 (Fig. 2). This depolarization of exciting and scattered light beams was caused by birefringence phenom￾enon due to the presence of anisotropic tetragonal domains with the z axes forming the angle of 458 with the EexkE2 direction (Fig. 2) [12]. Thus, only the EexkE1 geometry could be used for polarized Raman spectroscopy exper￾iments with tetragonal single crystals. Polarized spectra in Fig. 8a, 1 proved the equiprobable orientations of t0 domains along the three C4 cubic axes in nonstressed samples. Only one 265-cm21 line was registered in the k spectrum, while the rest five tetragonal modes were observed in the ’ geometry. This is consistent with the calculation results presented in Table 2 for the PB; D; F column. Thus, the Raman spectra shown in Fig. 8a, 1 allowed us to reliably divide the Raman line of the A1g-mode (265 cm21 ) from Fig. 8. The polarized Raman spectra at 300 K of the as-grown ZrO2 – (Eu2O3) (8 mol%) (a) and ZrO2 –(Gd2O3) (8 mol%) (b) single crystals. 1 and 2 are the scattering geometries with the excitation electric vector EexkE1 and EexkE2; respectively (according to Fig. 2). 1108 A.A. Sobol, Y.K. Voronko / Journal of Physics and Chemistry of Solids 65 (2004) 1103–1112