A series of ferroelectric glass-ceramics was elaborated by the controlled growth of Ba(1-x)Sr(x)TiO(3) crystal particles in the glass system 60[Ba(1-y)Sr(y)]TiO(3)-10Al(2)O(3)-30SiO(2)(0≦y≦0.2) in molar basis. Analysis of crystal
phases by X-ray diffraction revealed that Sr content in Ba(1-x)Sr(x)TiO(3) increased with increasing content of SrO in glasses by its preferential transfer into the crystal phase, and the appropriate temperature for the crystal growth was 1100°C. Curie temperatures of glass
-ceramics shifted to lower temperature with increasing SrO content in the crystal and comparatively high dielectric
constant was obtained at room temperature for a glass-ceramics with y=0.2. Frequency dependences of dielectric constant and loss tangent were examined in the frequency range from 1 K to 1 M Hz

O-oka, Kazuo

Oda, Kiichi

Yoshio, Tetsuo

Okayama University Scientific Achievement Repository

Memoirs of the School of Engineering, Okayama University Vol. 17, No.1, February 1983. Preparation and Dielectric Properties of(Ba,Sr]Ti03-Alz 03-SiOz Glass-Ceramics* * *Kiichi ODA , Tetsuo YOSHIO , Kazuo O-OKA(Recei verl December 13, 1982)SynopsisA series of ferroelectric glass-ceramics was elabo-rated by the controlled growth of Bal Sr Ti03 crystal-x xparticles in the glass system 60[Bal_ysry]Ti03-l0AlZ03-30SiOZ(O~~O.Z) in molar basis. Analysis of crystalphases by X-ray diffraction revealed that Sr content inBa1 Sr Ti03 increased with increasing content of SrO-x xin glasses by its preferential transfer into the crys-tal phase, and the appropriate temperature for the crys-tal growth was 1100°C. Curie temperatures of glass-ceramics shifted to lower temperature with increasingSrO content in the crystal and comparatively high di-electric constant was obtained at room temperature fora glass-ceramics with y=O.Z. Frequency dependences ofdielectric constant and loss tangent were examined inthe frequency range from 1 K to 1 MHz.1. IntroductionGlass-ceramics is a material fabricated by controlled growth of crys-talline phase in a glassy matrix and its properties reflect those ofthe crystalline phase. Ferroelectric materials can be prepared bygrowing ferroelectric crystalline phase in a glass article. Manyinvestigations were carried out to develop ferroelectric glass-ceramics. th' .. 1 h 0' 1 . 1-4)1n e var10US compos1t1ona systems, suc as Ba -T102-A 203-S102* Research Institute for Non-Crystalline Materials9798 Kiichi ODA, Tetsuo YOSHIO and Kazuo O-OKAand Na2o-Nb20S-Si028).as dielectric materials. 1 .° 5, 6 ) b . Al ° S .° 7)sro-T~o2-A 203-S~ 2 ' P O-T~o2- 2 3- ~ 2Some of above systems are practically utilizedin condensers or other applications.Barium titanate, [BaTi03 ], is a representative ferroelectric materi-al and has been extensively studied as sintered ceramics9 ,lO) and glass-ceramics. The dielectric property of sintered BaTi03 at around roomtemperature is usually improved by addition of oxides such as SrO,CaO,ZnO and Zro2 , which shift its Curie points, Tc ' to lower temperatureby the formation of solid solutions, e.g. Bal Sr Ti0 3 . Thus, if the-x xsolid solution of Bal Sr Ti03 can be grown in glassy matrix, then a-x xuseful ferroelectric material can be prepared with high dielectricconstant, E , and low temperature coefficient of E at around room temp-erature. The present experiments were conducted to confirm above pre-diction and a new glass-ceramics with crystalline phase of Bal Sr Ti03-x xwas successfully elaborated in the system 60[Bal_ysry]Ti03-l0Al203-30Si02 ·This paper describes preparation of the glass-ceramics, analyis ofcrystalline phases grown at various temperatures, determination of thecomposition of Bal Sr Ti03 solid solution and dielectric properties-x xof the present glass-ceramics.2. ExperimentalGlass composition studiedTable 1Reagent grade chemicals of BaC03 , srC03 , Ti02 ,Al20 3 and Si02 wereused as raw materials. These chemicals were mixed to obtain glasseswith compositions shown in Table 1and the mixtures were melted in Pty=O=0.067=0.1=0.125=0.167=0.260[Bal_y5ry]Ti03-10A1203-305i02(mol %)B5-0B5-1B5-2B5-3B5-4B5-55amplecrucible at l4000C for 2 hr in anelectric furnace. During melting,glass melts were stirred by Pt rod.--------------------Melts were then poured on a stain-less steel plate and disc samplesof 20 rom in diameter and 2 rom thickwere obtained by cutting and pol-ishing. Samples were then heat-treated to grow crystal phase for---~--------------1 hr at various temperatures rang-ing from 760° to l200°C.X-ray diffraction analysis was performed by X-ray diffractometerand microstructure was examined by Scanning Electron Microscope.Preparation and Properties of (Ba,Sr) Ti03·AI,03·SiO, 99Dielectric properties were measured by Impedance Analizer.Fig.l DTA curves of test glasses.oEBS-3BS-SBS-lBS-O1000(OC)900800..c~3. Experimental Results and Discussion3-1. Differential thermal analysisDTA curves for some glass samplesare shown in Fig.l. Three exother-mic peaks are observed, a sharp peakat around 830°C and two broad peaksat around 930° and 1030 0C. All ofthose exothermic peaks are due tothe crystallization of glasses.The sharp exothermic peak at around830°C shifts to higher temperaturewith increasing content of SrO inglasses.3-2. Microstructures of glass-ceramicsScanning electron micrographs are shown in Fig.2. Microstructuresare similar for all samples heat-treated at 11000C for 1 hr and Bal _xSrxTi0 3 grains are almost uniform in size(0.2 ~m in diam.).BS-l BS-3 BS-S 1 ~mFig.2 Fracture surfaces of glasses heat-treated at 1100°C for 1 hr.3-3 Crystalline phases grown at various temperatures(1) Crystal phases grown in BS-O(y=O) glassX-ray diffraction patterns are shown in Fig.3 (a)-(e). No signifi-cant diffraction peaks are observed for the sample heat-treated at 760°c, and two crystal phases appear for the sample heat-treated at 800°C100 Kiichi ODA, Tetsuo YOSHIO and Kazuo O-OKA50UUU: Unidentified crystalT: BaTi035 :,a-BaSi20SH :,Il-BaAI2Si20e (Hexagonal)402 e(0) Cu-KOt30. T(UdHS5T H5T(Ju)Jjhs 5T H5I I(a)20Fig,3 X-ray diffraction patt~rns of B8-0 glass heat-treated atvarious temperatures for 1 hr.(a) -760°C, (b) BOOOe,(c) 900 oe, (d) 1000oe, (e) l200 0 e° . 2 2d(obs.)(A).I/I o (%),l/d{obs.),l/d(cal.),(hkl)3.1372 33 0.1016 0.1016 (102)2.7715 21 0.1302 0.1300 (110)2.3382 5 0.18290.1752 (200)2.2981 .7 0.1893 0.1883 (112)2.0691 10 0.2336 0.2315 (202)1.6529 9 0.3660 0.3660 (114)1.6474 5 0.3685 0.3700 (005)Indexing of the unidentifiedcrystal powder pattern as ahexagonal lattice.Table 2, one is BaTi03 ~~d another isunidentified. A.nalYsis of theunideqtified peaks, assuming itto be a hexagon~lcrystal, yieldsits lattice parameters of° °a=5.543 A and c=B.220 A, whichis close to thos~of hexagonalbenitoite-type crystal(BaTi8i30 9° ° 4): a=5. 50 A, c=B. 32 A) , as shownin Table 2. In addition, thefact that the diffraction peaksof the benitoite-type crystaldisappear when the sample sur-d 0face is abraded, implies the a=5.543 A, c=8.220 Acrystal growth at the surface of glass. Main crystal phases grown inthe glass heat-treated at 900 0 e or higher are identified as BaTi03 ,S-Ba8i20 5 and S-BaA128i20 B( Fig.3 (c)-(e)).Preparation and Properties of [Ba,Sr JTiOs-AI 2 0s-Si02 101(2) Crystal phases grown in BS-I-S (y=O. 067-0.2) glassesIt is recognized that three identified crystal phases appear inthese glasses when they are heat-treated in the temperature range from900° and 1200°C. X-ray diffraction patterns of glasses heat-treatedat 1100°C for I hr are shown in Fig.4 (a)-(c). Two crystal phasesobserved are S-BaSi 20 S and S-BaAI 2Si 20 S ' another is Bal _xsrxTi03 whichpeaks shift to higher angles with increasing content of SrO in glass.That is, Bal _xsrxTio3 solid solution, S-BaSi20 S and S-BaAI2Si 20 S aregrown by the heat-treatment at higher temperature.(aUTHS 5T H5T(ubHT 5 5H5(C1dJ)HS5 TT H5I I20 30T: (Ba,SrlTi03S:~-BaSi205H:_-BaAI2Si20a( Hexagonal)TI I40 502 e(0) Cu-KD< 60Fig.4 X-ray diffraction patterns of BS-0,-2,-S glasses heat-treated atllOOoC for I hr. (a) BS-O, (b) BS-2, (c) BS-S(3) Composition of Bal Sr Ti03 solid solution-x x .The phase diagram of the system BaTio 3-srTi0 3 was determined byBasmajian and Devriesll ) They indicated that the solid solution ofBaTi0 3 was formed in full composition range of the system and 3/a~cdecreased with increasing amount of SrTi03 . Based on their results,present authors calculated the composition of Bal Sr Ti03 as follows.-x x3/a~CBaTiO _3~srTiO3 3where,3/a~c was calculated using the d-values, dIll and d 211 .x3~ 3~a,CBaTiO - la7CBa Sr TiO3 I-x x 3102 Kiichi ODA, Tetsuo YOSHIO and Kazuo O-OKAThe relationship between y(Sr/Sr+Ba)in the glasses and x(Sr/Sr+Ba) inthe crystal indicates that Sr in theglass preferentially transfers intothe BaTi03 during heat-treatment( Fig.5 ).2a2c·0.50.40.3x0.20.1o 0.1 0.2 0.3yFig.5 Plot of x in Bal _xsrxTi03 vs.y in 60[Bal_ySrylTi03-l0A1203-30Si02 glasses heat-treatedat 1100°C for 1 hr.150 L...-_...J.... ---I.... ---I. _150100Temp.(OC)50Temperature dependence of Efor test glasses heat-treatedat 1100°C for 1 hr.• 85-0300 ·85-1085-2.. 85-3iii .. 85-4c:: a 85-50uu 250.;:-UCIJ4i0200Fig.63-4 Dielectric properties(1) Dielectric constant, ETemperature dependence of E ofthe samples crystallized at 11000Cfor 1 hr are shown in Fig.6. Thefigure indicates that T decreasescwith increasing content of SrO inthe glasses, and E at Tcseems tohave a minimum(at y=0.125), that isE at T decreases with increasingcamount of SrO in glass(0~~0.125).Beyond y=0.125, it conversely in-creases(0.125<y~0.2). The de-creaseof Tcwith y is caused by theformation of Bal Sr Ti03 • The-x xcompositional dependence of E at Tcmay be taken for the product of twofactors, amount of Bal Sr Ti03 in-x xsample and its E •Preparation and Properties of (Ba,Sr) Ti0 3 -Alz0 3 -SiOz 103Amount of crystal grown in the glass increases with increasing amountof SrO, and E at T of Bal Sr Ti03 decreases with increasing of x.c -x xConsequently, the product of these factors is likely to give above non-linear relation.Values of E obtained in the present work are lower than that of theglass-ceramics in the system of BaTi03 ( E=500) obtained by Kokubo etal. 2). This is due to smaller particle size and smaller amount ofcrystal, which results from the suppression of crystal growth by highercontent of Si02 in the present glass.(2) Curie point, TcT of the crystallized BS-O glass is l60°C, which is higher thancthe Tcof BaTi03 , l20°C. Generally, Tc of crystal shifts by impurities, applied stress and grain size of crystal. In the present work, noimpurity is contained in BaTi0 3 crystal grown in BS-O glass and appl-ied stress to the crystal particles is very small because its tetra-gonality, represented as cia ratio, is 1.015, which is almost identicalto that of BaTi03 single crystal. The shift of Tc in this case islikely to be the result of small particle size( 0.2 ~m in diam.).Ulrich and smoke13 ) obtained Tcof 150°C for BaTi03 prepared by theheat-treatment of spray welded glassy BaTi03 • They considered thatthe shift of T is attributed to small grain size, 0.2-0.5 Vm.c(3) Variation of E and tano with frequencyVariations of E with frequency are shown in Fig.7. In frequencyrange from 1 K Hz to 1 MHz, E decreases with increasing frequency.300iii 250e ~--u.;:U..a:;Ci 200 lE::=L_10' 105Fr~q...~cy ( Hz ).85-0• 85-1·85-2.85-3• 85'4• 85-5--3.0""c'".... 2.0·85-0• B5-1• B5-2• B5-3• B5-4• B5-510' 105F..,qu~ncy( Hz )Fig.7 Frequency dependence of E oftest glasses heat-treated at1100°C for 1 hr.Fig.8 Frequency dependence of tanoof test glasses heat-treatedat 1100°C for 1 hr.104 Kiichi ODA, Tetsuo YOSHIO and Kazuo O-OKAlow T of 60°C is successfullycsolid solution as main crystalFig.8 shows variation of tano with frequency in the same range.Loss tangent of the crystallized glass slightly increases with in-creasing frequency, the same trend is observed in sintered ferro-electric ceramics. Comparatively high values of tano is caused bythe superposition of glassy matrix with high tano.4. ConclusionIn order to obtain glass-ceramics with T at comparatively low temp-cerature, a series of glass were prepared and they were heat-treatedfor crystallization. Glass composition in the present work was thesystem 60[Bal_ysry]Ti03-l0A1203-30Si02(0~~0.2),and heat-treatmentswere carried out at temperature ranging from 760° to l200°C. Varia-tion of E and tano were measured as a function of frequency in therange from 1 K Hz to 1 M Hz. Following results were obtained.1). A glass-ceramic with comparativelyelaborated, which contain Ba l Sr Ti03-x xphase.2). In the glass with y=O, crystal phases of BaTi03 , 8-BaSi205 and6-BaA12Si20S are grown by heat-treatment above 900°C, and in glasseswith O<y~0.2 three phases of Bal _xSrxTi03 , 8-BaSi 20 5 and 8-BaA12Si20S.3). It is recognized that SrO in the glass preferentially transfersinto BaTi03 during heat-treatment.4). T of glass-ceramics, where E shows maximum, reduce with increasingccontent of SrO, that is, y. This is due to the growth of Bal Sr Ti03-x x, the composition of which depends upon SrO content in glass.5). E at T have non-linear relation with x showing the minimum at y=c0.125. It is assumed that the non-linear relation comes out as theproduct of two factors, namely, increase of Bal Sr Ti03 amount and-x xdecrease of its E.6) In the range from 1 K Hz to 1 M HZ, frequency dependence of E andtano for the present glass-ceramic show the same trend as that ofsintered ferroelectric ceramics.5. References1) A.Herczog, J.Am.Ceram.Soc.,47,(1964)1072) T.Kokubo, S.Sakka, M.Tashiro, J.Ceram.Asso.Japan,74, (1966)5173) T.Kokubo, C.Kung, M.Tashiro, ibid ,2.§.,(1968)5234) T.Kokubo, C.Kung, M.Tashiro, ibid ,22,(1969)529Preparation and Properties of (Ba,Sr) Ti0 3 ·Alz0 3 ·SiOz 105L.K.Frevel, H.W.Rinn, Anal.Chem.,~,(1953)16975) W.N.Lawless, R.Radebaugh, R.J.Souleu, Rev.Sci.Instrum.,~,(1971)5616) L.G.Rubin, W.N.Lawless, ibid ,~,(1971)5717) T.Kokubo, H.Nagano, M.Tashiro, J.Ceram.Asso.Japan,22, (1969)2938) A.Herczog, Glass Ind.,~, (1967)4459) F.Jona, G.Shirane, "Ferroelectric crystals" Pergamon Press Inc.,(1962)24910) G.H.Jonker, Philips Tech.Rev.,!2, (1955)12911) J.A.Basmajian, R.C.Devries, J.Am.Ceram.Soc.,iQ,(1957)37312) H.Jaffe, D.Berlincourt, J.M.Mckee, Phys.Rev.,l05,(1957)5713) D.R.Ulrich, E.J.Smoke,J.Am.Ceram.Soc.,~,(1966)210

Preparation and Dielectric Properties of [Ba,Sr]TiO(3)-Al(2)O(3)-SiO(2) Glass-Ceramics

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