Document gb7LOOM64wx9ee5Mdkp30rRBQ

9 M'lC -----*--e^-i^LWfa: --"w - LEAD INDUSTRIES ASSOCIATION 0 SASY ASMS SYRSST NCW YORK 17* N. Y. August 21, 1959 SUBJECT: SUPPLBCTT3 TO "IEAD U TSE CERAMIC nHOSTRIES* To the Members of the Load Industries Assoelstlcnx Enclosed at * tlie third end fourth supplement* to our technical data hook. "lead in tbs Ceramic Industries." issued in December 1956. The third supplement, to be added to the "Glares" section of the book, is titled "Use cf Lead in Coatings for Ceraa&e Dielectric Bodies." The fourth supplement, to be added to the "Bodies" section, is titled "Use of Lead in Ceramic Bodies." These tvo supplements are being nailed to nore then 6,000 people connected vlth the ceramic industries vho have already received the bode, and vlll also be included vlth future copies of tha book sent out in answer to requests for it. These vlll b# followed by other supplaoents fra time to time. Very truly youm. Secretary '^ Sao S' w w..ny,-ajneMM y' *  1 ^i<wuyajB--W"^iig.wwvji-Uwni ' ".' ,11.MW.,, -*:jMJt L IA22518 USE OF LEAD IN COATINGS FOR CERAMIC DIELECTRIC BODIES* The need for coatings or glaze* for km dielectric \o%% compositional change* to determine those compuii- ceramic*. which possessed and maintained high uf- non* Hiih the highed electrical surface resistivity. face rcsidivity under high humidity environment*, Although the literature provide* very limited infor hai been recognized for some time. Such a coated mation concerning the surface resistivity of glaze* a ceramic mud he of an equal grade to the uncoated number of reference* pertaining to glass surface* art ceramic CJAN-1-10 specifications! and mud he cap- mxcd. The problem involve* Ih o mechanisms, con hie of ea*y fabrication by conventional method*. ductivity in the coating and conductivity over the sur Some Ivpc* of organic coaltnp, f g, silicones. may provide lor iem(Hrar\ benefits. However, it h gc-*cfalty held that to attain the drured permanence, inorganic coalinp are a prerequisite. face of the coating. Solubility of the gU,1* ra Hater is of concern, e g., alkalies may he leached from the surface nhen th* glass n esposed to high humidities resulting in increased surface conductivity. A lead gla/e though containing alkali, may result in a tight On live had* of cMinMvc csalualton of many dilTcrent or more stable structure which restrict* thejnotioa gla/e opposition*, high lead gla/c* were found to ,if alkali knv I he moisture layer may be continuous he super**. I ead monosilieatc and lead Nsiltcalc or discontinuous, depending on solubility, structural were established as the best coating* in term* of groupings and the Hater layer itself, l.ead, a*.an in uater run-irff and ckvincal rcsidivity unde; humidity gredient of the coating is effective m reducing Haler ceding. stability and thus promoting non-wetting on the The injective in the research referred to above vn surface nd concurrent high surface resistivity. to develop a ceramic coating whose surface resistivity Psc measurement of electrical rcsidivity under high would fu*t he less than 7.5 * Mi megohms under humidity condition* was carried out in a cabinet m *>5 pe'ccnt relative humidit> The approach to this nhich the relative humidity and temperature could problem Has to study typical gla/c*. incofTK*rating he mamiaincd ciwdant. Any value above I01* ohm*, 1 as measured, was rcpielcd a* infinite resistance, This irsunc. r*<p^ird hs |.<hn It K>vn*c. f.t.'i4 i. WCr. id S DiViii intflHs .t miIi* ,f irva.h M ihr VS*t of kiicnv ihe Voir I nisrrHis. wivtr, the yn^xaip of the l S Arms Krwauii and fVxtupmciH i jhl |MC Che early wink eliminated many leadlcs* and low krad composition* and indicated the need for a high krad content m these coatirp. The esHnpositiom based on lead borate and lead nHHiosilicate exhibited C . .-** >. - c. i. N 1961.01 5 LIA22519 ' ii ^au uri `m (he best isatcr funtrfI and electrical surface rcsislivity. The lead Innate base coating appeared to potxru a higher degree of non-aemng characteristic* but 'Sc lead silicate have gla/et maintained their ifd* (tally high rcvstisiiy (hroughtHJl the led (f<0 da)1*). The lead borate and lead mooosilicate glue* pro vided dear. smooth glue*. Various additives produc* inf other texture* (mat and semi-mat) had little cfleet on non-*cttinf and electrical resistivity proper ties of (he base glare*. Numerous lest data sho%ed that lead monmilteaic uu the component necessary in the coating to o k t I the requirements. Some of the more interesting lead monoulkate coalinp are gives in Table 3-3. These provided the greatest reproduci bility in infinite surface rcsistivit) under high humid ity conditions. There *c t c also a number of other more complei outings invoking the use of small amount* of BcO. alkaline earth oxide*, alkaline earth zirconium vilicatev etc.. which also exhibited infinite surface re sistivity in the test*. The lead hisilKale and lead aluminosilicate (hisilicatc) ha>e coatings are equally promising and superior where acid resistance also of concern. Of interest also K (he self glue formed on the-- lcad alumimniltcate low shrinkage type ceramic at 1950 F. This self glare coaling ha* practical im portance since it possesses high water repellency andr ha% high rrvstjvii) under high humidity at character*-- bate of lead glue*. f 4 r :S l i. V J ll IDJIIJ h l w w j * ''xiw. *' ' \ -"yjm i i w t mj mtm i*y ******* USE OF LEAS IN CERAMIC BODIES* At noted previously in this section, kad oxide hat a number of interesting and increasingly important uses in ceramic bodies. This resume concerns primarily the lead fluxed electronic ceramic bodies. The unique properties developed and discussed herein may likely result in other than dielectric uses. l-cad oxide has found increasing use also in other electronic ceramics, e g., high dielectric constant, ferromagnetic, ferro electric. piezoelectric and semiconducting ceramics. For example, kad titanate may be added to barium titanate to increase the Curie temperature. Mixtures of lead titanate and lead /irconatc base found use because of their excellent electromechanical proper ties over a wide temperature range. Howcser, the im portance of kad in these other electronic ceramics v. ill he covered in laier supplements to this Manual. The ceramics covered in this paper are discussed in the following order: A. Ultra l ow Ceramic Dielectric* B. I ow or Zero Shrinkage Ceramics C. Other low Temperature Bodies ULTRA LOW LOSS CERAMIC DIELECTRICS Ceramic dielectric bodies generally contain a glass and one or more crystalline phases. The dielectric loss is largely due to the dielectric loss of the compo nent phases and in varying extent also to the cUeic loss of the ceramic hod). Therefore, in designing a low loss body the dielectric losses of the various phases and also the loss due to elastic causes should he minimized. The glass phase should contain ions, such as kad, with high valency and large electronic polarizability. The crystalline phase should not be piezoelectric. The proper amount of glass phase should he employed and good fabrication techniques to provide for a dense, void-free structure to prevent conversion of electrica' to mechanical energy. The dielectric constants of the crystalline phasc(s) and glass should he nearly the same. The ceramic body should he cooled slowly to provide for a moie stable configuration of the networks and ions. Early work showed woHasjonite to he an excellent crystalline phase. This type of irollatfomle ceramic, such as referred to briefly on page 2 of this Section, has provided lor the lowest loss characteristics yet noted for any flaw fluxed crystalline ceramic. Ihrt resume, p<rp*red by i4ui II. k*fWf. Fd*r4 S. and S (b\rta rnul'* of rrvmh at the Svh>s>! vt t<uni.ev Rotrrrv tbr Stair t'r.irf*->t, under the s (>k imUu p of the t. 1 Ai.t ij Krnaivb nj (Vtfinpmcar l h.NkU<nn Tfhle 7-1 shows the use of various amounts of lead fluxes (lead horatc and kad hisilicatcl in a wollastonite type ceramic. Table 7*2 shows the effects r `yay.'gT.i Jiqwujy iyiiwiniwinfwcimjg umu tw -- * iu j u T......' i___ _ . -l .: . t : -r .i-- ..i .i r m^i * r ^ 1961-02 *r r? ^ I-IA225 20 a\U*trniik**m^iJL*--m4ma--aa iintf^iafi a**i mi of quart; and alumina addition* to thi* type body. Table 7*) present* properties of kad fluxed wollavloniie bodies containing alkaline earth* and other additives- Table 7-4 show* the rr>mp*Jtinn of three kad fluxed woHasiomic bodies. the dielectric proper* tic* being measured at I, flfdlO. and 25d*K) mega* cycle*. In the absence of lead the toss factor faff* off to l.*3 at 25.000 megacycle* (See W factor* cor* responding to JAN-I-IO I. grade* in note under Table 7*11. The best body, fluxed with kad bisilicate, remain* L*5 at 25.f>00 megacycles. Table 7*3 pro vide** some summary data in lermx of specific compo sition* and include* strength values. Table 7-A shew* -- iqtawr^uaj'irniH'i muif111 the effect of kad flute* on a typical steatite body. These examples of ultra km toss diekctrie bodies are dependent upon the kad flux to supply the glass phase. LOW OR ZERO SHRINKAGE CERAMICS The objective in designing k>w or rcro shrinkage bodies is to provide for easier fabrication of parts shrrr extremely small tolerances are a prerequisite. Obvious))-, the mod desirable shrinkage mould be /era. The normal firing shrinkage which <vcur* in a [ *V*` lilglJ WU. C LlA??521 ry' LIA22522 w ' rani Hrff adtidH llfj " i ..................jn'mv" lumt^qeyp T i i f i ceramic is the result of nhxlur ically ami chemically ttvmhincJ walcr hemg Jnsen 4T, evolution of (j v i due to dissociation ol ran matcrta!v formation of glasses and or crystalline phawt of hi^ier tpcvifk' pravily, anJ filling of voids lo produce a matured ceramic </cro moisture absorption). Theie mecha nisms can result in firing t linkage up to JO percent. 1 he principle involved in developing a dense ceramic of zero firing shrinkage consists of incorporating into the ceramic composite a predominance of a crystal line phase and or a glassy phase H-hicfc upon firing wilt irreversibly invert to a phase of tower specific gravity; thus, this phenomenon compensates for the ir.hercnt firing shrinkage present in the body. Research ted to tno types of ceramic bodies pos sessing mo firing shrinkage, a spodumenc type and a lead aluminosilicate type composition. The ^vviunscnc type is not a true non-shnnkmg hody hut rath* under goes a tclativci) large fumg evpaosion reavtung a nuumum of 10 percent at I Tint F and then gradually u wiiinmini i.n jjj LIA2 25 23 *' -r.,> --' shrinks to the zero shrinkage rclciciwe line at ap proximately 2<KKJ F, see figure 7-1. Ol th. two c>mp4*smon\. the IcaJ tilunmn*s4lKutc IxxJy more vU*%cly approavbcs (he char jvterislics ol a due non-shrink ing type ccr^nnc. She firing shrinkage steadily in crease'. to a maximum ol atviut 2 percent at tMNI F and then giadudly expanJs up to the zero shitnkagc value at 2t#*l F. as shown rr Figure 7-1. Howeser, this |\pe hoJ> had to he fabricated at recalls cl) high pressure. It was later found that aJJilions of day to the \fi*dumcnc composition produced zero firing shrink age at nuvlcraie tahricalron pressu.es. Then, it was considcicJ that perhaps similar additions of da) as well as iMher vi*nvcniionjt cctannc materials is* the leaj alumim*M!kalc KxJy might prove promising am1 in Iasi. IcJ to low or esen zero firing shrinkage ccr .mscs lahtnatcsl at moderate pressures. Therefore, the lead aiumimisjlicate ct*mpi*sitK*n mas ch*wn as the ha>e formula fix this new apprivtcft to the problem. Over the range I7005 to 2000 F the P-2 body showed water absorption values *( 0.0$ percent or less. Once vitrified as the temperature is increased, the glass starts to bleed out resulting in sdf-gla/ing. This sell-glaze, being a lead aluminosilicate glass, d*xrx not delrail from ihe gix*d dielectric properties. Coatings of this type are highly desirable in main taining high resistivity under extreme conditions of humidity hx prolonged periods of lime. TaMe 7-9 presents summay data for the two ap proaches for the low shrinkage body. Systematic addition of pyrophyllite. clay, zircon, petalite. wollastomte and alumina were mode respec tively to this lead aluminosilicate have body in 5 per- tivr.|yxMi iiniM *t ti" s ' 2/ The Wad aluminosilicate diagram, sec Section If. Cage I. shovtk sessrai binary and ternary ei*mpoundv N*flie o.* i!k *s c mere prepared as NxJics *nj arc ; plotted i*n Figure 7-2; the areas of crystallization arc also shown, lab'e 7-7 shows the pr .'potties of v*mc t ;*t these lead aluminosilicate KxJicv I he m>*st promis ing N*d\ is ihc P-2 comp*sithwv Table 7-H sh*ms properties Ih P-2 and small rrKwJitkatH*ns o* this ii'nipMism in its (uither desclopment. This is Iruls more ol a m*n-shr inking hojy since il shnnks **n,\ about 21: percent, then expands and ufixs havk to the original size at maturity doe to the ik'sel**pnK*nt l a new crystalline phase tJ^VK percent Pho, percent M o , and 2*.M? percent Sj O.I. See I ijrurc 7-1. These Kdu*s haxc rut only low manuring temperatures but also U*ng filing ranges and fix'd dietedric priiperliex. s LIA22524 1 cent increments up to 60 percent additions in some eases. 1 hese specimens Here pressed using 8 percent moisture content (semi-dry pressing) and fired. The shrinkage data as presented in Figure 7-3 show the range pmsihlc from an expansion of 1.3 percent to shrinkage greater than 3 percent. The moisture con tent required for the l)pc forming operation influ ences the firing shrinkage. The P*2 type hody plus aa additive (which would compensate for the shrink age) Has evaluated for extrusion. plastic pressing, dry pressing, and casting. Table 7-10 thoni low shrink age compositions as designed for the various fabri cating `evhnkjues. OTHER LOW TEMPERATURE BODIES Lead Irtls h c ic used in fluting a large number of other Uh temperature bodies nhcre the crystalline portion contained one or more of the following: alumina. day. lyanite, spodumene. talc. wolU*tiinice. zircon. and /irconatcs. A number of highly interesting bodies Here developed maturing at low temperatures. An example of the type of expiratory work carried out ri gocn in Table 7-11. Zircon and several double silicates Here used as the crystalline phases in two lead fluxeJ hoJicv. the 10 percent clay being added for workability. It will be noted ifut all these KvJies mature at relative1) low temperatures. For example, the /ircsHt KsJ) A fluxed with .1 percent o* lead borate and HI percent clay has /eio ahw>rption at I KUO F. This is a grade L-4 body. y i The following data show titania fluxed with lead borate to provide bodies of higher dielectric coo lant. I .njw -w'mi M1 l 4 .! .1 ii 11 Jl i - i 1 it .i X . ! 'I T If *r 1 "T 'r 1' I I 1f iI ;i i 1 `I* *9 mw.-- i' ?**! A--^ V*S Tttania................... ........ . 69f.; 66 * cent stacks larger than 2 microns. Ajax SC has the l ead Borate................... . :i< 24'i large slack particles prrealrined at 1000 C. These fl.ll CUy........................ . 10'* l(T* materials, when fluxed with various lead frits, milled K .................................... . P.F................................... Moisture Absorption ('* 1 (1HOO-J9UO F) ......... 44 0.0041$ <0.05 51 0.00092 <0.05 in many interesting bodies. The Ajax P I plates) pro vides for very smooth surfaces. Some of the results are generalized at follows: 1. Using 10 percent Ajax P. 40-60 percent Ajax S and 30-50 percent of the lead aluminosilicate frit Those bodies matured nicely in the range of IHOQ'F (61.3 percent PbO, 3.1 percent A1.0lt 35.6 percent 10 1900 F. In the followi-ig data, calcined k)anitc was the prin cipal phae. the lead borate flux being held constant at 23 percent, and clay increasing at the expense of l > anile. Calc. Kvanitc.. I,cud borate .. Ball Clay 62' 15'. ?7` 23'* :o'; 52'i 23'* 25* SiOJ. bodies Here found to vitrify circa 2200*F for the higher fritted content. These bodies possessed good workability. 2. Using the calcined stacks (Ajax SC) in a simi lar series, matured bodies were obtained in the range 2 Jl*t* F to 2200 F for the higher trilled contents (40-50 percent) of the above mentioned lead alumi nosilicate frit. 3. In a series where the Ajax kaolins were the K .................. 6 til P.F................... 0.IMI1 III I..F................. 11.1X1061 Moisture Absorption (# ; > (IKOO-1900 Ft 0.05 5..M ll.Ull 10 0.00585 0.05 6.08 tl.OOl 1 i O.UO(75 0.05 principal compivicmv a number of bodies withut the composition range shown were grade I--4 at tem peratures of 2500 F to 2350 F. C'otn/Htuinm Hunur /.4}J Bodiri) Body S 0, .V These provided nicely matured bodies in the range of IKOO F to 1900 F. whi.h were t.-5 bodies. The civw/ollcd Ajax Laolms wee siud.cd extensively as the principal phases ol lead-fluxed ShJic s . Ihc Ajax T c<nsfsi% of 96 p^-fvcftl Laolimte plates and 4 percent stacks, all less than 2 nncr.*n. in st/c. The Ajax S is comp^ncd oi 30 percent plates and 70 per A> P .. _____ 22-35 24 26 Ah * m ........ 3MO 41 44 PW) B o ....... 0.20 25 30 BaCO ..... ____ 0-10 10 -- CaO> ... 0-10 -- -- MgCO. ... ........ 0-10 -- -- Ink ....... ---- pyiij^i I ;.m m.u* p i mujji.qp fjy ii ;[ ii i - ii <I ! t i i i ii H fr -t \ I W %JPWI I LIA22526 -------- -- : x i; l:: ii -i i -- aarf-awti Av' < mt i I Two composition* (38 and 52) when fired at 2350`F were grade L-5. These bodies provide for good strength and relatively lou shrinkage, since the stack. content is prr-calcined. The use of these con trolled materials also provides for very smooth sur faces as well as good dielectric properties. Some of the (cad fluxed wollastonite type bodies have been shown to provide for good impact resistance. A large number of bodies were studied involving 50-70 percent wollastonite, 30-50 percent clay, and 0-20 percent lead hiulicate and other additives. Table 7*12 presents data for one of the best of these bodies (B-32) in comparison with some high alumina bodies, the latter requiring considerably higher ma turing temperatures. The addition of lead flux to the wollastonite bodies generally improved their Impact resistance. The lead fluxed B-32 body, matured at 2OK0'5, had higher impact resistance (Charpy test| than a 90 percent Al.0, hod) fired to 2970*F Of approximately 9W F higher. The foregoing examples show the use of lead Buses in bodies to provide such properties as high strength, impact resistance, very smooth surfaces, good di electric properties, etc., at relatively low tempera tures. *******