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Properties of Calcium-Barium Titanate Dielectrics by Elmer N

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Properties of Calcium-Barium Titanate Dielectrics by Elmer N U. S. Department of Commerce Research Paper RP2025 National Bureau of Standards Volume 43, September 1949 Part of the Journal of Research of the National Bureau of Standards Properties of Calcium-Barium Titanate Dielectrics By Elmer N. Bunting, George R. Shelton, and Ansel S. Creamer Dielectrics having co mpo itions in the system 3CaO:TiO,-BaTi03-TiO, were matured at 1,260° to 1,500° C. Data are given for the compositions, heat-treatments, absorption, shrinkage, and for K, the dielectric constant, and Q, t he reciprocal of the power factor, at 25° C for frequencies of 50, 1,000 and 20,000 kilocycles per second and for 3,000 megacycles per second when ]( is not greater than 50. Values of K were also determined at 1 megacycle per second for variou tem peratures from - 60° to +85 ° C. Lowest valu e. of Q (and highest of K ) were associated with specim ens of high bari a co ntent. Linear t hermal expan­ sion (25° to 700° C) ra nged from 0.65 to 0.87 percent. The pecimens of some compositions were unstable and cha nged in 1C and Q values with time. I. Introduction II. Preparation of Dielectrics and Methods of Test This paper is the third of a series dealing with ceramic dielectrics compo ed of titanium dioxide Dielectrics having the compositions shown in and the oxides of the alkaline earth elements. A figure 1 were prepared from reagent quality car­ study of these titanate systems previollsly re­ bonates of calci um and barium and the commercial ported [1, 2] 1 revealed di electrics of diverse grade of titania (grade TMO) used in the prepara­ properties that find application in the fi elds of tion of the other alkaline earth titanate dielec­ electronic instrumentation, particularly where the trics [1, 2]. A chemically pure grade of titania space factor is important, as in hearing aids and (99 .9%) was used in the preparation of a few speci­ other special circuits. These dielectrics are also mens for compari on purposes. The methods of valuable for the production of capacitors for usc preparing these dielectrics and of determining 0 at temperatures above 150 0, where paper and TiOZ electrolytic capacitors do not function satis­ factorily. A rather limited amount of information has been published by others [3, 4] on the electrical prop­ erties of the calcium-barium titanates. However, it is desirable to investigate these materials for a wide range in composition so that a more complete knowledge of their properties will be available. Because the temperature coefficient of the dielec­ tric constant for calcium titanate was known to be negative, it was expected that many of the calcium-barium titanate dielectrics might have a negative coefficient. Also, the low electrical-loss C3 TL-~~ __~ __~~ __~ __~ ____~ __~ 70% coo BoO 70 % character of calcium titanate indicated that a 300;. TiO z TiO z 30°/. large portion of the fi eld in this sys tem would FIGU RE 1. Ternary diagram f01· system CaO-BaO-Ti02 probably behave similarly. showing compositions studied. 1 Figmes in brackets indicate the literature referen ces at the end of tbis D=BaO; C = CaO; '1' = '1' iO,; thus, D,'1',=2DaO :3'1' iO,. e, Decrease in paper. J( and Q with time; ct, decrease in J( and increase in Q with time; 0 , stable. Calcium-Barium Titanate Dielectrics 237 their properties have been previously described constant K , and reciprocal of the power factor, Q, [1,2). of the matured specimens. The data for a given III. Results and Discussion composition are considered to be the most repre­ In table 1, data are given for th e composition, sen tative among those obtained from measurf\­ heat-tr eatmen t, absorption, shrin kage, dielectric ments of 3 to 11 test sp ecimens. TABLE 1. Composition, heat treatment, absorption, shrinkage, dielectric constant K, and Q oj bodies ~n the system 3CaO:TiO,-BaTi03-Ti0 2 Composition Dielectric co nstant I( at .Reciprocal, Q, of power weight Heat treatmen t 25 ° C and- factor at 25° C and- _._-----,-----' Proportion of ------- Specimen en d mem bers Xo. I )[0. 2 Ab· Sh rin k· designation or join, weigh t ___________ _ St~~~' age percent 50 1,000 20 3,000 50 1,000 20 BaO CaO TiO, Tom. Tern. 3,000 ko/s kc/s mc/s mc/s kc/s kc/s me/s mo/s PC I'- Time per- T ime ature ature ---------------------------------------------------- CaO:6TiO,­ BaO:18TiO, °C hr ° C hr % % CT6............... 100 I..... ... - .~ .. 1~5 8~5 1, 100 1 .1 ,275 1 0.00 16. 5 117 117 117 1, 700 1, 900 2,400 18BC6........ .... _. 33 67 6.5 3.5 90 1,100 1 1,275 1 .00 15.4 86 86 86 600 1,000 1, 800 BTI8 ...................... _ 100 9.6 90.4 1.100 1 1. 275 .00 15.0 75 74 74 260 1, 000 7, 000 CaO:2TiO,· B aO:fiTiO, CT2 ___ ... _..... _... 100 26.0 74.0 1,100 1 1,310 .00 18.0 142 141 141 1. 900 1,200 1, ROO 6B C2 .............. _. 73 27 6.5 19.0 74. 5 1,100 1 1,300 .01 15.6 107 107 107 700 500 1,000 6BC5............... 43 57 13.0 12.0 75.0 1, 100 1,310 .00 17. 1 84 83 83 3,000 1, 400 2,700 6BC8 ....... ..... _.. 20 SO 19. 5 5. 5 75.0 1, 100 1. 275 .00 16.4 60 60 60 3,000 4,000 10, 000 6BC9 ........ _. ... .. 5 95 23.0 1. 5 75. 5 1, 100 1 1,275 .00 15.9 49 49 49 48 2, 000 10,000 10, 000 960 BT6 ....................... 100 24.3 7,1. 7 1, 100 1. 275 .00 13.7 46 45 44 39 8,\ 400 2,200 490 2CaO:3TiO,· BaO:4TiO, C2T3 .......... __ . .. 100 31. 9 68. I 1, 100 1,310 . 00 17.9 151 151 151 2, 000 1. 000 1, 600 BC22............... SO 20 6. 5 25. 5 68. 0 1, 100 1,300 . 06 15.8 115 114 114 700 300 700 BC24............... 60 40 13.0 19. I 67. 9 1, 100 1,295 . 01 18. 3 88 87 87 1. 000 1. 000 1, 500 B026.............. 40 60 19.5 12.7 67.8 1,100 1,290 .00 16. 8 68 68 68 2, 000 1, 600 4, 000 BC27_..... ... _... 3n 70 22.7 9.6 67. 7 1, 100 1 1,290 .00 17.2 60 60 60 2, 700 1, 800 10, 000 BC28.......... ..... 20 80 25.9 6.4 67.7 1, 100 1 1,290 .00 17.2 51 51 50 47 2, 600 4, 000 10, 000 940 B C29 .... _.... _.... 10 90 29. 2 3. 2 67.6 I , 100 1,290 .00 16.9 44 44 43 42 2,700 1,900 5,000 2,100 BT4 . ................... ... 100 32.4 67.6 1. 100 1 1,330 .00 15. 1 34 34 35 34 1, 600 2, 000 3, 700 2, 600 CaO: 1.8TiO,· BaO :5TiO, 5BC8_. ............. 18 82 22. 7 5. 0 n 3 1. 100 1,285 . 00 17.0 56 56 56 560 600 1. 000 5BC9.............. 9 91 2·5.2 2. 5 72.3 1,100 1,28.1 .00 16.0 49 49 49 700 550 850 5BC95 ............ __ 5 95 26. 5 1. 2 72. 3 1, 100 1, 285 .00 15.1 45 45 45 750 770 1, 000 BT5 ....................... 100 27. 7 72. 3 1. 100 1 1,325 . 04 12.0 39 37 37 1, 500 2, 300 1, 300 CaO.TiO,· BaO:3TiO, CT_.. ...... _...... _ 100 ............ __ 41. 2 58.8 1,100 1, 400 1 0.01 16.7 143 14~ 143 2, 000 3,500 SOD BC2 ........ ....... 83 17 6. 5 34. 4 59. 1 1, 000 1,320 5 "2.65 18.3 115 11 2 lU9 20 59 225 BC3 ............... 70 30 11.7 28.9 59.4 1, 000 1,320 >\ 1, 62 19.4 112 110 107 25 90 570 BC,1.... __ ....... 50 50 19.5 20.6 59.9 1,000 1,275 2 0.00 19. 0 !H 94 94 1,300 1,200 1, 100 BC6 ...... _........ 40 60 23.4 16.5 fill. 1 1,100 1 1,290 .04 16.6 H2 82 81 600 1, 400 2, SOD BC7 . ............. 30 70 27.3 12.4 60.3 J, l00 1 1,290 . 00 17.0 72 72 71 1, 600 2, 400 4,000 BC8.. ........... 17 83 32.4 7.0 60.6 1, 100 1, 290 .00 17. 0 57 57 56 3,800 3,400 10,000 BC9 .......... _.... 10 90 35.1 4.1 60.8 1,100 1,2f>O .00 17.7 52 52 51 50 2, 400 3, 600 10,000 1, 240 BT3 ...... _........ 100 39.0 61.0 1, 100 1,260 .03 17.4 44 44 43 42 650 720 SUO 460 238 Journal of Research TA BLE 1. Composition, heat treatment, absorption, shrinkage, dielectric constant K, and Q of bodies in the system 3CaO :TiO,-BaTi03- Ti02- Continued Oomposition D ielectric consta nt K at Reciprocal, Q, of power weight H eat treatment 25° C and- factor at 25° C a nd- P roportion of Specimen end members N O.1 N o.
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