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1.
Phase relations in the binary system K2 O-GeO2 were determined by conventional quenching techniques. Three compounds, K2 O.2GeO2 , 3K2 O.11GeO2 , and K2 O.7GeO2 , exist in the composition range 65 to 100% GeOn. The compound 3K2 O.1lGeO2 melts congruently at 1055°C, whereas K2 O.2GeO2 and K2 O.7GeO2 melt incongruently at 761° and 950°C, respectively. Thermal expansion data for the crystalline compounds are presented. The structure of potassium germanate glasses is discussed. 相似文献
2.
E. F. RIEBLING P. E. BLASZYK D. W. SMITH 《Journal of the American Ceramic Society》1967,50(12):641-647
Density and viscosity results are presented for ternary Na2 O·GeO2 ·B2 O3 melts (∼600° to 1300°C) and glasses containing as much as 35 mole % Na2 O. Synthetic partial molar volume models indicate a fairly broad stability region for BO4 tetrahedra in the B2 O3 -rich melts. Similar models for GeO2 -rich melts reveal a more limited stability region for GeO6 octahedra. The expansion coefficient contours and viscosity isotherms confirm the volume-based conclusions for the liquid state. The high-temperature volume models were used to develop glass volume models that agree to within several percent of experiment. It has been concluded that the melts and glasses possess similar structures. The relatively greater compositional stability of GeO6 octahedra in the presence of B2 O3 (compared to Al2 O3 ) can be related to the smaller average number of oxygens around boron (III), at a fixed O/Ge ratio, compared to aluminum (III). Evidence is presented for a slight decrease of the thermal stability of GeO6 octahedra in the GeO2 -rich melts above about 1000°C. 相似文献
3.
Phase equilibrium relations in the system Li2 O-GeO2 were determined using standard quenching techniques. In contrast to published literature five congruently melting compounds were found to exist. They are Li2 O·7GeO2 , 3Li2 O O·8GeO2 , Li2 O O·GeO2 , 3Li2 O O·2GeO2 , and 2Li2 O.-GeO2 . The melting points, respectively, are 1033°± 5°C, 953°± 5°C, 1245°± 15°C, 1125°± 15°C, and 1280°± 15°C. Simple binary eutectic relations exist among the compounds. The eutectic temperature between 1:7 and GeO2 is 1025°± 1h0°C at about 96.8 wt% GeO2 ; the eutectic temperature between the 1:7 and 3:8 compounds is 935°± 10°C at about 90.9 wt% GeO2 ; the eutectic temperature between the 3:8 and 1:1 compounds is 930°± 10 °C at about 89.8 wt% GeO2 . Liquidus data for compositions richer in lithia than the 1:1 compound are only approximate because of the difficulty of quenching them; the phase relations between the 1:1 and 3:2 and between the 3:2 and 2:l compounds, however, are found to be of the simple binary eutectic type. The glass–forming region was also determined. Melts allowed to cool in air crystallized. When, however, the melts were quenched, glasses containing as much as 8 wt% GeO2 could be prepared in 5–g quantities. Both the refractive index–composition and density–composition curves for the glasses showed maxi–mums at about 6 to 8 wt% Li2 O. 相似文献
4.
Nong M. Hwang Robert S. Roth Claudia J. Rawn 《Journal of the American Ceramic Society》1990,73(8):2531-2533
The phase equilibria of the systems SrO-CuO and SrO-1/2Bi2 O3 were studied by X-ray diffraction analysis of quenched powder samples. The compounds SrCuO2 and Sr2 CuO3 melt incongruently at 1085° and 1225°C, respectively. The newly found compound Sr6 Bi2 O9 decomposes at 965°C into SrO and Sr3 Bi2 O6 melts incongruently into SrO and liquid at 1210°C. SrBi2 O4 undergoes a phase transition at ∼825°C, and although both are nonstoichiometric, the low-temperature phase is slightly poorer in SrO with 33.5 mol% SrO than the high-temperature phase. 相似文献
5.
Subsolidus phase equilibria in the system La2 O3 -P2 O5 were established. The system contains six intermediate compounds having molar La2 O3 :P2 O5 ratios of 3:1,7:3,1:1,1:2,1:3, and 1:5. It was found that the 3:1 compound has a phase transformation at 935°C. The 1:2 compound decomposes to a mixture of 1:1 and 1:3 at 755°C. The 1:3 compound melts incongruently to 1:1 and liquid at 1235°C and the 1:5 compound melts congruently at 1095°C. None of the lanthanum phosphates have lower temperature limits of stability. 相似文献
6.
Kazuhiro Narita Yoshihiro Takahashi Yasuhiko Benino Takumi Fujiwara Takayuki Komatsu Takeshi Hanada Yoshihiko Hirotsu 《Journal of the American Ceramic Society》2004,87(1):113-118
Some K2 O-Nb2 O5 -GeO2 glasses are prepared, and their crystallization behaviors are examined. 25K2 O·25Nb2 O5 ·50GeO2 glass with the glass transition temperature T g = 622°3C and crystallization onset temperature T x = 668°3C shows a prominent nanocrystallization. The crystalline phase is K3,8 Nb5 Ge3 O20,4 with an orthorhombic structure. The sizes of crystals in the crystallized glasses heat-treated at 630° and 720°3C for 1 h are °10 and 20–30 nm, respectively, and the crystallized glasses obtained by heat treatments at 620°-850°3C for 1 h maintain good transparency. The density of crystallized glasses increases gradually with increasing heat-treatment temperature, and the volume fraction of crystals in the sample heat-treated at 630°3C for 1 h is estimated to be ∼35%. The usual Vickers hardness and Martens hardness (estimated by nanoindentation) of 25K2 O·25Nb2 O5 ·50GeO2 glass change steeply by heat treatment at T g , i.e., at around 35% volume fraction of nanocrystals. The present study demonstrates that the composite of nanocrystals and the glassy phase has a strong resistance against deformation during Vickers indenter loading in crystallized glasses. 相似文献
7.
SiO2 -Al2 O3 melts containing 42 and 60 wt% A12 O3 were homogenized at 2090°C (∼10°) and crystallized by various heat treatment schedules in sealed molybdenum crucibles. Mullite containing ∼78 wt% A12 O3 precipitated from the 60 wt% A12 O3 melts at ∼1325°± 20°C, which is the boundary of a previously calculated liquid miscibility gap. When the homogenized melts were heat-treated within this gap, the A12 O3 in the mullite decreased with a corresponding increase in the Al2 O3 content of the glass. A similar decrease of Al2 O3 in mullite was observed when crystallized melts were reheated at 1725°± 10°C; the lowest A12 O3 content (∼73.5 wt%) was in melts that were reheated for 110 h. All melts indicated that the composition of the precipitating mullite was sensitive to the heat treatment of the melts. 相似文献
8.
MARK R. DE GUIRE T. R. S. PRASANNA GRETCHEN KALONJI ROBERT C. O'HANDLEY 《Journal of the American Ceramic Society》1987,70(11):831-837
Solid-state equilibria at 1000°C were determined in the Fe2 O3 -FePO4 -Co3 (PO4 )2 -CoO area of the Fe-Co-P-O system in air. Two new ternary compounds were observed: CoFe(PO4 )O, an oxyphosphate which melts incongruently at 1130°C, and Co3 Fe4 (PO4 )6 , an orthophosphate which melts incongruently at 1080°C. The ramifications of the liquidus behavior for the formation of rapidly solidified cobalt ferrite from cobalt ferrite-phosphate melts are discussed. 相似文献
9.
Structural Similarities Between a Glass and Its Melt 总被引:2,自引:0,他引:2
E. F. RIEBLING 《Journal of the American Ceramic Society》1968,51(3):143-149
It is suggested that the large expansion coefficient increase that occurs near T g , for mixed oxide glasses is related to cooperative thermal displacements involving polyanionic clusters in the liquid state. This is illustrated by the striking relation between melt isoexpansion coefficient contours and structure for these ternary oxide systems. It is also shown that the molar volume dependence on composition for a series of oxide glasses can be quite similar to that observed for their liquid state analogs. The adjusted melt partial molar volume models can be used to develop realistic glass models, suggesting structural similarities between an oxide glass and its corresponding high-temperature melt. Recently acquired evidence for alkali borogermanate compositions indicates a shift toward the right for the GeO6 ⇄GeO4 equilibrium in GeO2− rich melts at relatively high temperatures. Thus, an exact structural correlation between an oxide melt and its corresponding glass may, in some cases, be limited to temperatures below T g +Δ T (where ΔT ~300° to 400°C). 相似文献
10.
Phase equilibrium relations in the system Na2 O-GeO2 have been determined using standard quenching techniques supplemented by differential thermal analysis. Two congruently melting compounds, Na2 O·GeO2 and 2Na2 O·9GeO2 , exist; the melting points are 1103°± 15°C and 1073°± 3°C, respectively. The eutectic temperature between GeO2 and 2Na2 O·9GeO2 is 950°±f 10°C at 94.5 wt GeO2 . The eutectic temperature between 2Na2 O · 9GeO2 and Na2 O·GeO2 is 790° f 10°C at about 75 wt% GeO2 . Both the refractive index and the density of glasses in the system Na2 O-GeO2 exhibit maximum values at about 16 to 18 mole % Na2 O. The Ge-O-Ge absorption band at 890 cm−1 shifts toward lower wave numbers with the addition of Na2 O. 相似文献
11.
E. F. RIEBLING 《Journal of the American Ceramic Society》1966,49(1):19-23
Viscosity and density data were obtained up to 1700°C for a series of binary aluminoborate melts that contained as much as 15 mole% (∼21 wt%) Al2 O3 and up to 1620°C for pure molten B2 O3 . Large expansion coefficient decreases and a slight activation energy increase for B2 O3 above 1400°C suggested a tightening of its structure. The addition of Al2 O3 reduced viscosity and increased activation energy. The decreased compositional dependence of molar volume (compared to SiO2 additions) and the increased expansion coefficients accompanying Al2 O3 additions suggested a loosening of the O—B—O structure at 1600°C. Molar volume deviations from ideality were similar to but smaller than those for SiO2 and GeO2 additions at 1300°C. Microclustering of aluminum-bearing polyhedra appeared to occur at slightly higher boron atom contents than with SiO2 and GeO2 additions. 相似文献
12.
Phase relations in the system Sc2 O3 -WO3 were characterized. Two stable binary compounds were, found. The 1:3 compound, SC2 (WO4 )3 , melts congruently at 1640°±10°C and forms a simple eutectic with WO3 at ∼90 mol% WO3 and 1309°+10°C. The 3 : 1 compound, Sc6 WO12 , forms a simple eutectic with the 1:3 compound at -69 mol% WO2 , and 1580°+10°C. The melting temperature of SC6 WO12 was >1600°C. 相似文献
13.
The phase relations for the Sc2 O3 -Ta2 O5 system in the composition range of 50-100 mol% Sc2 O3 have been studied by using solid-state reactions at 1350°, 1500°, or 1700°C and by using thermal analyses up to the melting temperatures. The Sc5.5 Ta1.5 O12 phase, defect-fluorite-type cubic phase (F-phase, space group Fm 3 m ), ScTaO4 , and Sc2 O3 were found in the system. The Sc5.5 Ta1.5 O12 phase formed in 78 mol% Sc2 O3 at <1700°C and seemed to melt incongruently. The F-phase formed in ∼75 mol% Sc2 O3 and decomposed to Sc5.5 Ta1.5 O12 and ScTaO4 at <1700°C. The F-phase melted congruently at 2344°± 2°C in 80 mol% Sc2 O3 . The eutectic point seemed to exist at ∼2300°C in 90 mol% Sc2 O3 . A phase diagram that includes the four above-described phases has been proposed, instead of the previous diagram in which those phases were not identified. 相似文献
14.
The system BaO-TiO2 was investigated using quenching, strip-furnace, and thermal techniques. Five compounds were found to exist in the system: Ba2 TiO4 , BaTiO3 , BaTi2 O5 , BaTi3 O7 , and BaTi4 O9 . Of these, only barium metatitanate (BaTiO3 ) melts congruently (at 1618°C.). The dititanate melts incongruently at 1322° C. to yield BaTiO3 and liquid; the trititanate melts at 1357°C. to yield BaTi4 O9 and liquid; the tetra-titanate melts to TiO2 and liquid at 1428° C. The nature of melting of the orthotitanate could not be determined accurately because of the high temperature involved and the rapid reaction with platinum. The two eutectics in the system occur between Ba2 TiO4 and BaTiO3 at 1563°C. and between BaTi2 O5 and BaTi3 O7 at 1317°C. The temperature of the cubic-hexagonal transition in barium metatitanate was determined as 1460°C. and the transition has been shown to be reversible. The transition temperature is raised sharply by the addition of a small percentage of TiO2 although the extent of solid solution is quite limited. Some applications to the manufacture of titanate bodies and to the growth of single crystals of barium metatitanate are discussed. 相似文献
15.
The quenching technique was used to study subliquidus and subsolidus phase relations in the pseudobinary system Na2 Ti2 Si2 O11 -Na2 Ti2 Si2 O9 . Both narsarukite (Na2 TiSi4 O11 ) and lorenzenite (Na2 Ti2 Si2 O9 ) melt incongruently. Narsarsukite melts at 911°±°C to SiO2 +liquid, with the liquidus at 1016°C. Lorenzenite melts at 910°±5°C to Na2 Ti6 O13 +liquid; Na2 Ti6 O13 reacts with liquid to form TiO2 and is thus consumed by 985°±5°C. The liquidus occurs at 1252°C. 相似文献
16.
Phase relations in the binary system between SiO2 -P2 O5 and SiO2 were investigated by the quenching method using sealed platinum tubes to prevent the loss of P2 O5 . The compound Si02 -P2 O5 exists in two forms, the low-temperature β form inverting sluggishly but reversibly to the high-temperature β form at 1030°C. The β form melts congruently at 1290°C. The compound 2SiO2 -P2 O5 melts incongruently at 1120°C to a silica-rich liquid and SiOa -P2 O5 . In the region between 5 and 25 mole % PO2 , reactions were so sluggish that no data could be obtained by quenching. 相似文献
17.
Niall J. Donnelly Thomas R. Shrout Clive A. Randall 《Journal of the American Ceramic Society》2009,92(6):1203-1207
It is demonstrated that the use of ∼0.9 mol% Li2 CO3 (LC) as a sintering aid for Sr, K, Nb modified Pb(Zr1− x ,Ti x )O3 (PZT) ceramics is effective only in the presence of excess PbO (∼2 mol%). It is shown that LC and PbO react to form the compound, Li2 PbO3 (LPO) which has a melting temperature of ∼836°C. Using dilatometry, we were able to correlate shrinkage during heating of a green ceramic to the melting of the LPO. Consequently, complete densification and sizeable grain growth are achieved by solution-precipitation of the ceramic through the liquid phase. Importantly, sintering is not particularly effective with such small additions of either LC or PbO alone. In confirmation of this model, the LPO compound was presynthesized and used as the only sintering aid in the same PZT composition. The densification behavior of this mixture compared well with the case of separate additions. 相似文献
18.
Quantitative Identification of Phonon Modes Controlling the Multiphonon Relaxation in Heavy-Metal Oxide Glasses 总被引:1,自引:0,他引:1
Yong Seop Han Jay Hyok Song Jong Heo † 《Journal of the American Ceramic Society》2004,87(7):1381-1383
The phonon mode(s) controlling the multiphonon relaxation (MPR) in PbO–Bi2 O3 –Ga2 O3 glass was analyzed, and the effect of GeO2 addition on the MPR process was investigated. MPR rates were obtained from the lifetimes of the Tm3+ :3 H 4 level in glasses over the temperature range 20–280 K. In PbO–Bi2 O3 –Ga2 O3 glass, phonons from the bending vibration between GaO4 tetrahedra (∼550 cm−1 ) controlled the MPR process. On the addition of GeO2 , the phonon mode at ∼770 cm−1 due to the stretching vibration of GeO4 tetrahedra started to affect the MPR process. Phonon modes controlling the MPR process in PbO–Bi2 O3 –Ga2 O3 –GeO2 glass were both 550 cm−1 and 770 cm−1 . 相似文献
19.
Phase relations in the systems alkali monotungstate-tungsten trioxide were investigated in the range 600° to 1100°C.In the Li system, compounds with an A2 O/WO3 ratio of 1:2 and 1:4 are stable and melt incongruently at 745° and 805°C, respectively. In the Na system, the 1:2 compound melts congruently at 746°C, whereas the other 2 sodium tungstates (1:4 and 1:6) melt incongruently at 835° and 913°C, respectively. The K system includes compounds of 1:2, 1:3, 1:4, and 1:6 which melt incongruently at 684°, 842°, 912°, and 964°C, respectively. Eutectic points between the 1:l and 1:2 compounds in these respective systems are at 692°C and 56 mol%WO3 , 622°C and 56.3 mol% WO3 , and 633°C and 63 mol%WO3 . In the Rb and Cs systems, the 1:2 and 1:3 compounds form complete solid-solution series, and their melting temperatures increase with increasing WO3 content, respectively, from 690° to 868°C and from 732° to 902°C. The 1:6 compounds are also stable in these systems and melt incongruently at 1040° and 1046°C, respectively. 相似文献
20.
The effect of P2 OS on the devitrification of binary lead silicate glasses containing 64 and 59 mol% PbO was studied. Glasses underwent isothermal crystallization treatments at 400°, 450°, 500°, and 550°C. A polymorph of 3PbO2 SiO2 was the major product of crystallization for all compositions of glasses. Secondary products of crystallization were found to be a polymorph of PbOSiO2 in the 59 mol% and a low-temperature polymorph of 2PbOSiO2 in the 64 mol% PbO glasses. Dominant mode of crystallization in both binary glasses was surface devitrification at all temperatures studied. Addition of P2 O5 promoted internal crystallization in the form of spherulites. 400°C was found to be the most effective temperature for nucleating spherulitic growth. Crystallization at 400°C led to high concentrations of spherulites in all glasses containing at least 0.5 mol% P2 O5 . Concentrations of 0.5 mol% P2 O5 were needed to produce detectable levels of spherulitic nucleation at r<400°C. 相似文献