Doping effect of CrO 3 on crystallization and dielectric behavior of strontium titanate borosilicate glass ceramics (original) (raw)
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Dielectric and microstructural behaviour of strontium titanate borosilicate glass ceramic system
Bulletin of Materials Science, 1995
65(SrO.TiO2) 35(2SIO2.B203) wt% glass was synthesized. Differential thermal analysis study shows one exothermic peak which shifts towards higher temperature with increasing heating rate. Glass ceramics prepared by controlled crystallization of strontium titanate borosilicate glass produce uniform distribution of crystallites in a glassy matrix. Attempt was made to crystallize strontium titanate phase in this glass ceramic. Different phases precipitated out during ceramization have been identified by X-ray diffraction. It appears that due to high reactivity of SrO with B20 3, strontium borate crystallizes as principal phase followed by TiO2(rutile) and Sr 3 Ti 2 0 7 phases. Dielectric constant of these glass ceramics was observed to be more or less temperature independent over wide range of temperatures with low values of dielectric constant and dissipation factor.
Bulletin of Materials Science, 1996
Glass of the nominal composition 64wt~?,,(SrO-TiO2) 35wt%12SiOe. B2031 1 wt%(CoO) was prepared. The glass samples were subjected to heat treatment at 900 and 950 C. The phase progression in these glass ceramics from X-ray diffraction studies shows the formation of Sr2B205 as primary crystalline phase followed by rutile {TiO2). SryTi20 ~, SrB2SieO ~ and SryB2SiO ~ as secondary phases. The first DTA exothermic peak of glass corresponds to the crystallization of Sr2B205, rutile and Sr3TieO. phase while second crystallization peak may be assigned to the formation of SrBzSi20 s and Sr.~ B2SiO ~ phases. From mlcrostructure studies we find that strontium borate grows with larger grain size whereas the other phases like Sry"1"L,O., TiO: appear smaller m size. Cobalt oxide content in the strontium titanate borosilicate glass ceramic gives the thermal stability to dielectric behaviour and decreases the dielectric loss.
Bulk transparent barium strontium titanate borosilicate glasses in glass system (65-x)[(Ba 0.6 Sr 0.4).TiO 3 ]-30[2SiO 2 .B 2 O 3 ]-5[K 2 O]-x[A 2 O 3 ], A ¼ La, Fe (x ¼ 2, 5 and 10) were prepared by rapid melt-quench technique and subsequently, converted into glass ceramics by regulated heat treatment process. The phase identification was carried out by X-ray powder diffraction and their surface morphology was studied by scanning electron microscopy. The dielectric properties were studied by impedance spec-troscopic technique. Investigated glass samples were crystallized into major and secondary phases of Ba 1.91 Sr 0.09 TiO 4 and Ba 2 TiSi 2 O 8 , respectively. A very high dielectric constant having value upto 68000 was found in glass ceramic sample BST5K10F. This high value of dielectric constant was attributed to inter-facial polarization, which arose due to conductivity difference among semiconducting crystalline phases, conducting grains and insulating grain boundaries. Donor dopant La 2 O 3 and acceptor dopant Fe 2 O 3 play an important role for enhancing crystallization, dielectric constant and retardation of dielectric loss in the samples. Moreover, higher value of dielectric constant and lower value of dielectric loss was found in Fe 2 O 3 doped samples in comparison to La 2 O 3 doped samples.
Crystallization Kinematics and Dielectric Behavior of (Ba,Sr)TiO3 Borosilicate Glass Ceramics
Perovskite [(Ba 0.6 Sr 0.4 )TiO 3 ]-[2SiO 2 -B 2 O 3 ]-[K 2 O]-La 2 O 3 glass was prepared by conventional melt quench method. The differential thermal analysis (DTA) was performed on glass sample in the temperature range from 100˚C to 1000˚C by different heating rate to study the crystallization kinematics. The kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass samples were subjected to appropriate heat treatment schedules for their suitable crystallization. X-ray diffraction analysis (XRD) of glass and glass ceramic samples were done to check the amorphous state and crystalline nature. XRD of glass ceramic sample shows the major perovskite phase of BaTiO 3 (BT) along with the formation of secondary phases Ba 2 TiSi 2 O 8 (BTS) and Ba 2 Ti 2 B 2 O 9 (BTB). Scanning electron microscopy (SEM) is also studied to see the morphology of the grains of major and secondary phase formation in BST glass ceramic samples. La 2 O 3 is played an important role to increase the nucleation of the crystallites in the glassy matrix. The addition of La 2 O 3 results in development of well interconnected crystallites formed as major phase of BST. In this paper, we are reporting the crystallization behavior of BST borosilicate glass system and high temperature dielectric characteristics of their glass ceramics.
Lead bismuth titanate borosilicate glasses were prepared in the glass system 65[(Pb𝑥Bi1−𝑥)⋅TiO3]-34[2SiO2⋅B2O3]-1La2O3 (0.0 ≤ 𝑥 ≤ 1.0) doped with one mole percent of La2O3 via conventional melt quench method. The amorphous nature of glass samples in this glass system is confirmed by using X-ray diffraction (XRD) study. Differential thermal analysis (DTA) has been employed to determine the glass transition temperature, 𝑇𝑔, as well as crystallization temperature, 𝑇𝑐. DTA measurements were recorded in temperature range from 30 to 1200∘ C. The prepared glasses were crystallized by regulated controlled heat treatment process on the basis of their DTA results. These samples are carried out for XRD measurements in the 2𝜃 range from 20 to 80∘ to study the crystallization behaviour and phase formation of the glass ceramic samples. The scanning electron microscopy (SEM) of these glass ceramic samples has been carried out to explore the morphology through nucleation and growth of the crystallites in the glassy matrix. The values of dielectric constant as well as dielectric loss were increased with increasing the temperature within the frequency range from 20 Hz to 100 Hz. The addition of 1 mol% of La2O3 to the lead bismuth titanate glasses enhances the crystallization and acts as donor dopant for this glass system.
Bulletin of Materials Science, 1997
Glasses in the system (65-x) [SrO'TiO2]-(35) [2SiO2"B203]-(x) [Bi20 a] where x = l, 5, 10 (wt%) prepared by melting in alumina crucible (1375-1575 K), were subjected to different heat treatment schedules followed by DTA studies. Crystallization study showed the formation of Sr2B205 as major phase at low temperature (.~950°C) heat treatment. At high temperatures, TiO 2 and SrTiO 3 with or without Sr2B20 5 crystallize out depending on heat treatment. In this paper, the influence of variation in composition, thermal treatment on the nature of crystallizing phases as well as on the resulting microstructures are investigated through XRD, IR and SEM. Uniform crystallization was achieved by suitable addition of Bi20 3 and proper heat treatment.
Dielectric Properties of La2O3 Doped Composite (PbxSr1−x)TiO3 Borosilicate Glass Ceramic
Journal of Ceramics, 2013
Ferroelectric (PbxSr1−x)TiO3 (PST) perovskite phase has been crystallized in borosilicate glassy matrix with a suitable choice of composition and heat treatment schedule. La2O3 is a donor dopant for PST and can make it semiconducting. Dispersion of semiconducting perovskite phase in insulating glassy matrix in glass-ceramic samples may lead to the formation of space charge polarization around crystal-glass interface, leading to a high value of effective dielectric constant, εr. Therefore, with the aim of the developing glass ceramics with high dielectric constant, glasses in the system 64[(PbxSr1−x)O·TiO2]-25[2SiO2·B2O3]-5[K2O]-5[BaO]-1[La2O3] have been prepared (0.5≤x≤1). It is found that the addition of La2O3 strongly affected the crystallization and dielectric behavior of glass-ceramic with PST perovskite phase. All glass ceramic samples show a diffuse broad Curie peak in their εr versus T plots. Curie peak temperature, Tc, depends on compositions of the glass-ceramic samples as ...