**8. Acknowledgments**

The authors are grateful to Dr. Goeuriot D. and Dr. Liébault J. (E.N.S.M.), to Prof. Kortov V.S. (Ural State Technical University) for the supply of some samples. Fruitful discussions with Dr. Bernardini J. (Im2np) and Prof. Fakhfakh Z. (LaMaCoP) were highly appreciated. The first author gratefully acknowledges financial support from the Ministry of Higher Education and Scientific Research of Tunisia and the French Institute of Cooperation.

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**25** 

V.P. Ilyina

*Russia* 

*Academy of Science* 

**Evaluation of Dielectric Properties from** 

**Electrical Porcelain Production** 

*Establishment the Karelian Centre of Science of the Russian Academy of Sciences Institute of Geology of the Russian* 

**the Cakes of Feldspathic Raw Material for** 

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

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

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

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°

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 physico-

a common source of mineral products which has some advantages over pegmatite.

the glass phase of the resulting ceramics [1,2].

technical properties of feldspathic rocks are shown in Table 1.

**1. Introduction** 

raw material [1].

С for 3 hr.

