**1. Introduction**

578 Sintering of Ceramics – New Emerging Techniques

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Feldspars are anhydrous alumosilicates containing alkaline (Na+, К+) and alkaline-earth (Са2+) cations. The basic types of feldspars used in ceramic production are: potassic feldspar (microcline) К2О•А12O3•6SiO2, sodic feldspar (albite) Na2O•Al2O3•6SiO2 and calcium feldspar (anorthite) СаО•А12О3•2SiO2. The dielectrical properties of electrical porcelain depend on the mineralogical composition, alkali ratio and total alkali content of feldspathic raw material [1].

To examine new sources of raw materials for electrical porcelain production, we have evaluated nonconventional types feldspathic rocks of Karelian. Feldspathic rocks such as alkaline and nepheline syenites from the Elisenvaara and Yeletozero deposits, aplite-like granite from the Louhi area and volcanics such as Kostomuksha halleflinta and Roza-Lambi quartz porphyry. On a chemical compound they represent Alumosilikate K, Na, Ca, less often Ва. Form isomorphic numbers, including Plagioclase [3]. In world practice, the above rocks are a common source of mineral products which has some advantages over pegmatite.

Nonconventional types of feldspathic raw materials were evaluated on cakes because the dielectrical and other properties of natural feldspars and their cakes are much the same, while the chemical bonds of natural feldspars persist after their melting and are inherited by the glass phase of the resulting ceramics [1,2].

Cakes (material in vitreous state, as in ceramics) were prepared from finely ground (particle size 0.063 mm) powders of deferrized feldspathic rocks by caking them in crucibles at 1350° С for 3 hr.

We have assessed the electrical properties (dielectrical permeability -ε, dielectrical loss angle tangent -tgδ and electrical resistance -lgρ), the thermal coefficient of linear expansion (ТCLE) and рН of nonconventional types of feldspathic raw materials such as potassic halleflinta, quartz porphyry, syenite and granite-aplite and compared them with those of pegmatite, a common paw material for ceramics production. The compositions and physicotechnical properties of feldspathic rocks are shown in Table 1.

Evaluation of Dielectric Properties from

Chaupino-Louhi

White Sea

Louhi

Mamsko-Chauiscoe

Central

Kazakhstan Karaotse-

Uralskoe Malache-

Finland Кеmio (FFF) 18 8.0

Table 1. Mineral structure and properties of feldspar breeds.

Priladozhye Jccima

Kalevala Kostomuks

Feldspar deposits Mineral structure,

Hetolambino, Uracco, Civ-guba

Area Deposits №пп Q Mi Pl <sup>Ε</sup>

Lypikko 4 5 27.2

Yeletozero 11 29.1 Or-

*Slyudozero* 12 22.0 Or-

Mamskoe,B.

1 2 3

2,5 28.6 24.2

27.8

70.0 64.1 61.3

49.8 46.6

Uljlega Cjryla 6 7.1 58.0 34.9 7.00 2.10 0.027 7.90 8.84

Roza-Lambi 7 44.0 44.2 11.8 5.40 0.85 0.160 8.08 7.10

Louhi Yeletozero 9 23.1 53,5 31.4 6.65 1.51 0.032 7.83 9.80 Priladozhye Elisenvaara 10 2.8 43,0 54.2 3.26 2.00 0.025 8.00 8.25

Type of breeds

Pegmatite

Volcanic rock

Syenite

Graniteaplite

Pegmatite-granite

the Cakes of Feldspathic Raw Material for Electrical Porcelain Production 581

*mass. %* Dielectric properties

27.5 7.3 14.5

23.0 25.6

ha 8 24.2 68.0 7.8 7.50 1.23 0.050 9.15 10.0

Northern 13 9.0 71,0 20.0 7.5 - - 7.78 -

lgskoye 16 2.5 58,7 38.8 7.7 - - 7.76 -

vskoye 17 43.6 29,3 27.1 5.6 - - 7.80

55.0

Enskoe Rikolatva 14 10.1 69,5 26.4 7.0 - - 7.52 8.4

Asia Ljngarskoe 15 15.5 47.7 36.8 5.6 - - 7.82 -

37,0 50,0

50

7.70 7.53 7.35

6.20 6.73 - 0,94 1.00

0.95 1.00

30,8 40.4 3.87 0.85 0.207 7.89 7.98

11,1 66.9 4.02 1.32 0.034 7.84 9.76

450 - - - - 8.3

83

ρ◌ּ 1010 Ohm◌ּ cm

> - 0.148 0.062

> 0.900 0.127

ТКL R◌ּ 10-6 1/ grad

tg δ 4000С

7.70 7.93 7.72

8.10 8.51 рH

9.67 9.08 9.85

9.83 9.82
