Document 4vRzD3kQ57Exb82zpQ3KN0mYV

LIfv22207 kSOM LEAD INDUSTRIES ASSOCIATION 0 I CAST ASMS STRICT NCW YORK IT. N. Y. | ewn 'fsesweewssn* u i.ii in i rimW C- I i Kerch 10, 1954 SUBJECT! SUPPLEMENT TO "LEAD TK THE CHUMIC INDUSTRIES* To Kaabers of tha Load Industries Association! BidoMd Is ths second supplement to our technical data book, "Lead in the Ceraolc Industries," issued in Decenber, 1956* This supplement covers "Low-Tenperature Glasses as Bending Miterlala for Crystals." This is being nailed to all of the 5,000 people connected with the ceraeic industries who have already received the book and will also be Included with future copies of the book sent out in answer to requests for it. It will be followed by other supplements from time to tims, see* of which are already in preparation. Very truly yours. 0 5#cr*t*ry. L l( IIU n**wppwrj`f*fug"<i"|n_i*uri.1 <; LIA22208 J C T P W W W I" .... ............... .. m i ' ............ nnaH M "i|ia LOW-TEMPERATURE CLASSES AS BONDING MATERIALS TOR CRYSTALS MECHANICAL AND PHYSICAL FUNCTIONS The principal application* of low-temperature flawe* at bonding materials for crystals fall into (he following caitpYiei. 1 a I Claw h used a* a supporting medium for crystal* -to hold a crystal in place or to male possible a desired configuralion or thape for a number of crystal*. If temperature and other factor* are not important thit purpose it seised by Ittharpe-gkcerin or other cements: hut if elevated temperature and low dielectric km or high turface resistivity are important, then low-temperature flatte* arc ettentlal. |h It h sometimes devrahk lo disperv cr>*laU with reawmahlc uniformity throughout a given volume. and lo maintain the dittrihution. Ferroelectric materials. for example, mat he dispersed in a number of media, often organic plastics: hut km-temperature glasses offer ohtiiHtt advantage* Inm the tiewpoint* of thermal characlcritfwt and geometric or dimenskmal stability met a period of lime, icI Ihe agglomeration of small crystal* into larger maw * constitutes an c-sscmL'. commercial application f km-temperature glasses The most prominent uch application it that of apgktmcrating powdered mica lacitutlv tcr> wnall crystal** into glass-bonded mica, a ceramtp(at>ic which mat he molded and machined. Tttanatcv ferrites. wollwonitc. and a large number ol other matcrialt mat be to agfksmcraicd. tdt ll crttlalt are hooded with k>w.|emperatuir |l'o of high lead content, it rt jxwtthk lo increase Its density where thit it detirahk. tc Often, when large crystals are sealed into mclal hi* iNop. into flat* tube*, or into ceramic ca^t ihe teal matt he **lght" enough to promt passage of vaporv 01 it mutt be a true xacuum teal, I oWcmperalurr glasses arc. aO factor* considered. more satisfactory than ant other ..latcriak. If) The properties of horded cryMai guwtps or masses can often be greatly modified by proper chtwcc of flaw Kndcr Such propeniet at hardnett. thermal con ductivity. and thermal e\parvtk'O are influenced by the flaw tvndmg agent, tf I It it sometime* doiraSle to lute km -temperature glasses to ihe turfacet of crystals in order to modify turf ace cbafaclcntiicv crystal-bunding maleriaK ma> he isolated in the folkminf way*. (I If vokh ctitl in a tvwvded crystalline material uted in a high-voltage Acid, there a concentration of dcclrtitiatic line* of force at the void*, and corona discharge and arcing occur within the material. The heal deteloped result* in degradation of the Mituhiioa and may lead to complete breakdown, tb) Since water absorption decreate* volume mn* livit) and incrtivi diwipation factor. Ihe flat* birder, by Ailing void*, proem* *uch absorption. In the case mica, there h sometime* penetration of moisture akvng open lamination* unlett the mica plate* are surrounded In glass. A porous malcrul may he satisfactory in the absence ol high-soilage Addt and if used in a tacuum or an inett unxtfhcfc. hut lor moa low-tow applications Ihe imuUiK'n must he free of void*, tel There arc instance* where the electrical charac teristic* of a flatter* Wat composite mutt he nwvJiAcd. An ciampk it the ca*e where the dielectric constant must he raised. Thu can he ikme by using a flaw to food matciialt such a* titanium dioiide or Irtanatc*: and in this instance, at well at inherv a high-lead flaw an!* in increasing Ihe dielectric constant. REQUIREMENTS FOR LOW-TEMPERATURE BONDING CLASSES In order lo (unction pr*pcr!\. in terms of the physical and ckclrical need* outlined ahntc. hooding glasses must meet a considerable number W rather strict re tirement*. which, taken together, restrict seriously the choree* ol satisfactory glasses. These requirements mat he summarized at lolk*w*. 14014*4 --a *4 iai>K i ELECTRICAL FUNCTIONS While practical application* often Mitohr comhinataint of physical and electrical pu*pcnict, (he dec* local funcihUH id low-temperature glasses Vtcd at A 1 Mon*, k. Awctni profrwK of kyui\ Ne*ri Coitrfr if taiamMti. Nrtai, N, j. - ----------- - ---------- i * l i i................................................... N 1931.01 w iwgg.* .1 l iih \ . l U22209 Trrmrmm w u m w .iin i p m a m . i 'M i * l a f n ||u w ...... i i , n m (aI The (Uc\ muU he fluid at km temperatures, fcncull) than i2(KM.Vxr F and often below IUM F. (h) Inadditiontofluidity, the viscosity characteristics in certain icmpciaturc ranges control the usefulness of |Uwei. (cl Surface tension variation with temperature, espe cially in conjunction with viscosity. may he extremely important in crystal bonding. (dl For successful cry vial bonding. H h cvcitiat that the glass net the crystal. As a rule thtv involves wne degree of chetmcJ reaction although purrfy physical penetration h conceivable. tel Ah hough it n possible for dcvrtrifird glav% 4 certain types t Pyroceram. (or example to have dou- ahk physical and electrical characteristics, the glasses which have proved most satisfactory for bonding crystals do me destfnfy when used m the customary manner. fft In addition to then function of hltmg s o h Is to prevent phytic*! absorption or penetratMn <l water, glasses lor Kmdmg crystals must have gtxnl resistance kchemical reaction with water, tgl if a glass-crystal composite is to be used (or ctcc* tncal insulation. the glass binder must have km dielec tric k*s*es. except where a high dielectric ssmsiani is desired. Lvcn m this latter case the disupatum factM should he k*. fht For glass-crystal insulations the glass should have high surface and volume fesististtiev til The dielectric strength of a glass used for tswsdmg crystals shouU he high if the composite ts to act as an insuLaiivr in high-voltage hetdv t j I For many applicatMtnv, Kwvdirg glass must have goexa thermal shock resistance. For cs*tuai*n pur poses. this characteristic must be related to thermal expansion and thermal conductivity, as wdl as nthet properties. WiHirf t*ar* M<m * --X-- *aO aiti W >w .* mutm lht ** a l>a* |4m III With a few exceptions. the thermal expansion coefficients of glass and cry stal should be compatible. (It Optical properties of the bonding glass may Mxnctimes be important, particularly m the infrared and ultraviolet portion* of the spectrum. (ml Fix an increasing number of applications the bonding glass must not change or deteriorate greatly when subjected to nuclear radiations. 4 n I If a glass-crystal cotnpnile is to be employed for radiation shielding, the glass composition generally k one that contains a maximum of heavy ions, such as lead and barium. tot Where k*w density is a requirement (he hooding glass may have lo be composed of such elements as lithium, beryllium, and boron. tp) In those caves where glass-crystal composites arc empkned extensively : glasv-Nmdcd micas, for cxample I. often in relative!) large pieces, the cod of the bonding glass must he reasonable. CrthiOcriiHW of the properties and requirements bslcd aK*vc will indicate the complexity of the problem of developing suitable k>-temperature gtas^s for hod* mg crystals. MTTHODS FOR OBTAINING LOW-TTMPEAATULE CLASSES In the dcsek*pmcnt *f k*w-tcmpcraiute glasses for crystal bunding all of the fcst*gm/cd meihtxh tor "loosening" the glass structure arc utilized. Thc< methods based ufxxi sHreows silica as the most stable glass, are briefly summarized hrk*w. (1} flO triangles replace SK), leirahedra. If (he re placement is eompUte Kxatc glasses result. If partial, the glasses are Kxosilicales. U'bcfl it h necessary to keep the softening temperature km the K<ron muW he w ell in excess of the silica, and the glasses arc more properly called si|cuhoatcs. SunsJitutHsn if BO fx P,Ot lowers the softening temperature if phsKphate glasses. l!l The oxygen ratio tratio of oxygen atoms lo net* work-forming atoms! n mcrcavd. Ihe eflccis with siliwa glasses I for example. P,G^ replaces SrO.I art well likwn This mechanism n not applicable m the case of R O rrvxiibrd with SiO or P.O_ urxv the N*fi*o remains triangularly coordinated in Ihe prrv* ence of tetrahedral u Imw and letialiedral phnsphru1 he matte: is rust | p<acical Hnpvlirxt sieve com* metvia! k*w-temperature glasses contain alkalicv alka line earths, k-ad. z iik , barium, etc. ( 11 Ihe glass former rs replaced by one of larger si/c ih kmet valcncv. leaving (be oxygen ratio unchangedIhuv Si is replaced in part by It r AI, or by Ph m high lead glasses. In most kna-tempcralurc glasses, however, 1i and Al are added for reasons of chemical ................... mn'VJ "XI jjp S '** *&*** (' nt-rryirt durability and modification of other properties. lead glass composition appreciably, and thereby improve plays an important role. as discussed to the following properties lo the point where the glaum are socccsa- section. hut it is rarefy one of replacing a r*ctc*L ful commercially. former. Type /. ROB.Ol. The must commoe glass in this (4) Network mojiftcn arc atkM or exchanged. Two category is PbO-BjO,, although BaO-BtO, and PbO- acimns arc involved here- hrU, the addition of any R<0-H 01 art also found. The pure Wad borate glass j ekvirmalcot o ik Ic (alkali, alkalmc earth, lead, cine, has an excellent combination of physical and electrical etc. I iflcrtKt iht o&ygcn ratio. The betwixt former properties, although surface electrical propenies are bonds lo all of the introduced otygem. end fewer somewhat sensitive lo mnisiure. The high specific otygem arc bonded to two network formers (fewer grant) is occasional)) objectionable, oxygens ad at bridges). In the case of pure borate lead Kxate glasses of high lead content are used glassev the addition of cWclrovalent oxides at first eslensivelv for bonding crystals when the electrical produce Murder** |[iim because the borom mumr propenie* of the cumjxRrtc mud he considered. Tahte ; tcitahedral Cswxdmation. Tim action continue* up to *1 icsdu ascs the change of dielectric constant with an oil gen rat** of |.e*| (where thesxetically 7It per* compoulR " cent of the Kwoo torn are m triangular (ixndituun lbeorciicall), no gtaw is possible aK>ve an oxygen and '' pruxiM are in tetrahedral coordination); and ratal of about ).? (9i percent PbO. R percent B.O,). ahir thi\ ratwi the added oxygen* are non-bridging. Dissipation factors fix the abuse glasses remain Ion 1 he flaws therefore Nvomc progressively `softer.'* user nwssf ol the range of composition* but lend to Ihc other netwixk m-xlihcr action tnutlm the replacement *4 a modifier h one 4 higher fwncntial (Na replaced hlihvhi larger number of modi* increase at the high-lead end. Softening Icmp-taturc* fuse m been determined with accuracy, but range from VMk|4Wi T. with the k*w temperatures at the fieri i Na replaced In Na - K - IJ). highdead end. < 51 1 he in gem to the network iru> he replaced in If sufficient time is ilkwef, these glasses lend to read part by fliaxide nun Nnce the aciwsa imdin a change m the degree ol covaleney of the structural with crystals, and the cumpsHKioos may change v4k< oentls to aher tome of the properties. unit! tW), ictrahrdra. BO, triangles). the glasses If fliRxme is added to the hn< glas^s in the fixm become ~w*fier ** The efled on the nature of the bonds n 4nwn kin: v-o VI B-O 11 Al-O M-f r-o P4 He-O Brl 5<)S ionic. 50*; covalent RWR. VK* cosalcot 44'# hWKi 5*'i Ciisknt UAK. f7*; cos alenl KWlic, .I7f* cosalcot TV, some. I!*? covalent XV# some. Mr, cosaleni 5v; sonic. covalent bl'i sonic. cosalcot sonx. cmalent ol lead fluoride, fluonne replaces part id the oxygen in the BO and BOt uuits, in accordance with the filth mrtKkJ JiH ined f*x obtaining low temperature fUves Ibcse fluorine-modified glasses soften at tern* peraiurcs as k*w as 74 to l and air fluid at `.cmfxta- lures M rr.uch aNvsc ItM*)' f. 1 \p< 2~ The i-djrfioo of SiO to a PKVh O, ix BaO-B U glass has tie effect of increas ing chemical durability Howeser. the rrfraclixinesa g pmu: h w - . fft ppp1 y "m fj b* ngvm In general. |Uim used lor Kwding crystal* utilize ownKnaiaun of Ihc hr dr* ten dimmed above for decreasing rcfrartormcsk i mes or c l a s s e s Ihc Mkmmg cfamhcaiMU) don not by any mcam include all p*ss*>4c types of l*w -temperature glasscv Ii don. howncr. assemble a rcprcseotatne cron **claw of glaim which haic hern used. or have been fwopoinJ. ' hinders for cryvtali. In general, these glasses meet nnnwf) requirements for physical, chenuc.l, and ehvtrical properties, ahhough in a few cam the applications are somewhat mlrklcd (ab sence H miHsiure. etc.). In certain instance*. reaction between glass and crystal sufftextst to alter the 'H  < iafeitaaiai* PPLItATION |m incrca<v so lhat K>l 10 percent SOj is the I %pc V R O KO SHIj. The (oUtwinf glass, which h maximum permissible if the softening temperature fluid at 1300" F. is represeotatrie of this group: in he kept below I2W F. A typical composition h K.O, NarO, U.O 7* PhO S2% BaO. PhO 52 HtBO, 41 SiO, 41 S*0, 7 l.tpe 6; Rf(t-KO-B.Ot. The following glass is useful If a higher wtfi(flin| temperature h permitted-about 1400 F-fhc following is uikfaclor): PhO . 71*5 H.BO, 13 SiO, 14 lot hooding crystals, but ihe high alkali conlent pro duces high dielectric lots, and surface resistance h not good in a humid atmosphere. Ni.B.O, . 72<* K,CO, co ..M 14 7tpr 7. KO-flU/jOj. The following glass, reported /.v /n * HO-RjO-AlOfB.O . The RO is preferably in the literature, has a high alkali content <45.3 per PhO, RaO, or a mixture **( the two, although 7j iO cent Nt.O), which make* it untuned for applications with PhO is satisfactory. Ihe R O ma) he any of the where humidity is even moderate. Electrically, it is alkaliev with a mixture likely to fisc heller results. pxv because of the high alkali. A tsptol compHitKW time containing fluorine, him* NaPO, 7J*X - eser I is the fottowtog: Cryolite 21`i Sa.CO, CaO 12.5 125 PbO 2 K ihBp.^Oy lhc high .ll.lt content ct BaCO, 7 the glass fvhm is disadsaaiagciHiv It could, howesrr, AXOHl, 16 be used in a dry atmosphere: H.HO, M Monobasic sodium phosphate ))* Ihe widening temperature is about HtiO* F. Flcctncal properties art fairly pxW. fipr 4 HO-K.O Al U -StO.-BO . Again the RO puletahlv PhO. baO h a mixture. ihe R O is \a O. k O, or l.i O. or a mixture. Ihe hdlowing is a sain* factory glass: Feldspar pho 2HS : HJBO| 3K Ni.CO, 6 boras 67 />/h j V. Zrtt-BO -I'.fJA number of (Inev ol this type base been made. Ihe V.O_ tup to 20' | kwen th-* softening temperature appreciably. Ihew glawrs base thermal expansion coefficients of 45-50 a IO f per centigrade degree. The softening temperatures are as lo* as IIM! F typr to B .<i HO BprSiOrr O . If phtwphoric acid ts combined with asbestos, steatite, or mica, and the mixture is heated, a glass of this general type appears ti be formed. Ihe Kwsdmg is reasonably pxxl but A eomfx*siion conuming fluorine is little studs has bevn gisrn to (be mcchanicx of the Cryolite IIP"* Kwvdmg actam. SrO| 10 Ph.O, Feldspar H HO, 30 SUMMARY 15 35 Ihe number H glasses available for bonding crystals s Urge. MiKt of them faD into Ihe general categories Still another ei*mpi*sition is discussed. Many sanations are possible fir each type, H bo 35*- and ihe comfwsitums given are merely typical. hh'Hb PhO 30 all tyfVx the addition of flskmnc lowers the softening SiO. 10 tempriaiute, and thus tkvubles the number t*f Ispev Cryolite IO Ibe choice of a glass for bonding crystah b deter Feldspar 10 mined tva only by the softening temperature. Moisture Na,COt 5 resistance, dielectric bwsex. thermal expansion, spe Softening temperatures ;re in the neighfsirhis*d of cific gras ity, manufacturing pnvess. and iHher Iacton 13(10 I . I kvtrical properties arc goisJ. an* ~*tcn governing considerations. S V t t | i I J!H p, .iL