2368 E.R. Andrievskaya Journal of the European Ceramic Sociery 28(2008)2363-2388 F 200+Fr + m c L 24002400 22022 2000 2000 770+10 Tc(e) 2800 2800 260 L 2600 -2600 430+25 2200 2000 F+C 2000 2000 T+F mol 03 Yb.o mol 2900±30 00+302600 2200 T+F 780±10 F+M 1351020304050607080905 2° Fig. 2. Phase diagrams of the binary systems with hafnia and lanthanide oxides from terbia to lutetia:(a)HfO2-Tb2O3, 2(b)HfO2-Dy203, 122(c)HfO2-Y203, 54 (d)HfO2-Ho2O3, 154(e)HfO2z-Er203, 54(f) HfO2-Yb203, 54(g)HfO2-Lu2O3 154
2368 E.R. Andrievskaya / Journal of the European Ceramic Society 28 (2008) 2363–2388 Fig. 2. Phase diagrams of the binary systems with hafnia and lanthanide oxides from terbia to lutetia: (a) HfO2–Tb2O3, 122 (b) HfO2–Dy2O3, 122 (c) HfO2–Y2O3, 154 (d) HfO2–Ho2O3, 154 (e) HfO2–Er2O3, 154 (f) HfO2–Yb2O3, 154 (g) HfO2–Lu2O3. 154
E.R. Andrievskaya/ Journal of the European Ceramic Sociery 28(2008)2363-2388 2369 2600 2600 2200 22 80Pr3 2600 2800 2400 2000 20001 mol mol T 2500 T,C 2300 L+H X C+H 2000 C+b 8 mol Fig 3. Phase diagrams of the binary systems with hafnia and lanthanide oxides from lanthana to gadolinia: (a)ZrO2-La203,63(b)ZrO2-Pr203, 63(c)ZrO2-Nd203, 63 (d)ZrO2-Sm203, 63(e)ZrO2-Eu2O3, (f) ZrO2-Gd2O3 63(O)experimental points: ()thermal analysis in air under solar furnace; (O)single-phase regions. (O gions by the data of XRd and annealing and quenching. cies in the anion sublattice of Ln2- Hf2+r07-(/2) decreases in solid solutions of fluorite type. 237 The thermodynamic stabil y/2.The pyrochlore-type phases demonstrate concentration ity of the pyrochlore type compounds can be determined using limits of stability, which are shown in Tables 4 and 5, Fig 8. empirical rule, which identifies the ratio between ionic radii The pyrochlore-type phases and their solid solutions are formed R=(r+Ln/+*HD), which must be higher than 1.2. In accordance y zirconia or hafnia with cerium subgroup of REO (from La with Colong, 235 the average ionic radi for the pyrochlore- to Gd), while the rEo of yttrium subgroup form disorder type phases can be approximately calculated by additive rule
E.R. Andrievskaya / Journal of the European Ceramic Society 28 (2008) 2363–2388 2369 Fig. 3. Phase diagrams of the binary systems with hafnia and lanthanide oxides from lanthana to gadolinia: (a) ZrO2–La2O3, 63 (b) ZrO2–Pr2O3, 63 (c) ZrO2–Nd2O3, 63 (d) ZrO2–Sm2O3, 63 (e) ZrO2–Eu2O3, (f) ZrO2–Gd2O3; 63 () experimental points; () thermal analysis in air under solar furnace; () single-phase regions, () two-phase regions by the data of XRD and annealing and quenching. cies in the anion sublattice of Ln2−xHf2+xO7−(x/2) decreases in ч /2.235 The pyrochlore-type phases demonstrate concentration limits of stability, which are shown in Tables 4 and 5, Fig. 8. The pyrochlore-type phases and their solid solutions are formed by zirconia or hafnia with cerium subgroup of REO (from La to Gd), while the REO of yttrium subgroup form disordered solid solutions of fluorite type.237 The thermodynamic stability of the pyrochlore type compounds can be determined using empirical rule, which identifies the ratio between ionic radii R = (r3+ Ln/r4+Hf), which must be higher than 1.2. In accordance with Colong,235 the average ionic radii for the pyrochloretype phases can be approximately calculated by additive rule:
E.R. Andrievskaya Journal of the European Ceramic Sociery 28(2008)2363-2388 T, c(a) 2800 2600 2600 220 1800 00 Tb,O, 2800 H州 M+F 80H0O zr0.2040 T, cI(h) 2800 2400 4. Phase diagrams of the binary systems with hafnia and lanthanide oxides from terbia to lutetia: (a)ZrO2-Tb203, 6(b and c)ZrOx-Dy2O3, 63, 194(d)ZOz-Y20 6(e)ZrOx-Ho2O3, 63(f and g)ZrO2-Er203, 219, 221(h)ZrO2-Yb2O363
2370 E.R. Andrievskaya / Journal of the European Ceramic Society 28 (2008) 2363–2388 Fig. 4. Phase diagrams of the binary systems with hafnia and lanthanide oxides from terbia to lutetia: (a) ZrO2–Tb2O3, 63 (b and c) ZrO2–Dy2O3, 63,194 (d) ZrO2–Y2O3, 156 (e) ZrO2–Ho2O3, 63 (f and g) ZrO2–Er2O3, 219,221 (h) ZrO2–Yb2O3. 63
E.R. Andrievskaya/ Journal of the European Ceramic Sociery 28(2008)2363-2388 T.℃ m%,(b) HfO2-Ln2o3 2c4n23 2400 HOz-Ln2Oa 30 2000 1800 0.0840088009200960.1000.104 960.1000.104 Fig. 5. Dependence of melting temperature(a)and composition(b)for eutectics in the systems MeO2-Ln2O3 vs effective ionic radius of lanthanide(Table 2, RLn3+ and RMe are taken by Ahrens scale " (a) V,nm l(b) 05320 0.1415 05315 b 05210 05160 05155 Yb ErY Sm Nd La 05150 0.09 0.10 Yb ErY Sm Nd La Fig. 6. Dependence of lattice parameters(a)and volume of elementary cell(b)for the solid solution based on monoclinic ZrO2 vs ionic radius of dopant. 230 058:。N axls·c 0.518 0514 0514 0.510 (a) mol RO15 mol RO15 Fig. 7. Dependence of lattice parameters(a)and volume of elementary cell(b)for the solid solution based on tetragonal ZrO2 versus ionic radius of dopant. 179
E.R. Andrievskaya / Journal of the European Ceramic Society 28 (2008) 2363–2388 2371 Fig. 5. Dependence of melting temperature (a) and composition (b) for eutectics in the systems MeO2–Ln2O3 vs. effective ionic radius of lanthanide (Table 2, RLn3+ and RMe4+ are taken by Ahrens scale 257). Fig. 6. Dependence of lattice parameters (a) and volume of elementary cell (b) for the solid solution based on monoclinic ZrO2 vs. ionic radius of dopant.230 Fig. 7. Dependence of lattice parameters (a) and volume of elementary cell (b) for the solid solution based on tetragonal ZrO2 versus ionic radius of dopant.179