**3. Thermal Coefficient of Linear Expansion (ТCLR)**

Thermal coefficient of linear expansion (TCLR) is a parameter which shows thermal expansion upon burning of ceramic products.

TCLR was measured on a DKV- 4 quartz dilatometer on specimens, 55◌ּ × 5 m in size, produced by pressing ground rocks to a grain size of 0.063 mm and subsequent burning in a silitic furnace at 1350°С to reach the maximum density of the specimens. TCLR was

estimated using the formula: <sup>0</sup> <sup>6</sup> 0 10 <sup>1</sup> 55,5 10 1 /deg., *<sup>t</sup> l l ltt* α<sup>−</sup> <sup>−</sup> =× + × <sup>−</sup> where t0 is initial

measurement temperature, 20°С , tl is final measurement temperature, 400, 700°С; l0 is the original length of the specimen, mm, lt is specimen lengthening, mm; 5.5◌ּ (10-6- 1/deg. of the TCLR of quartz glass.

The highest TCLR values (9.15 and 11.75◌ּ 10-6 1/deg., respectively) are characteristic of halleflinta (cake no. 8) at 400º and 700ºC, respectively. Halleflinta differs structurally from pegmatite in having finely dispersed quartz, which contributes to intense dissolution of

Figure 2 shows that high microcline and plagioclase concentrations in feldspathic rocks are responsible for a low angle tangent of dielectrical loss in cakes: (no. 8) potassic halleflinta - 0,050, (no. 10) syenite - 0,025 – 0.032, (no. 6) and pegmatite (Cjryla) – 0.027- and increases their electrical resistance (Fig.3) -(1,23, 2,0, 2,10◌ּ 1010 Ohm◌ּ cm), which is consistent with GOST parameters 2484-85 for electrical porcelain: dielectrical permeability not more than 7, the angle tangent of dielectrical loss – 0.030 and electrical resistance 1-2◌ּ 1012. Low dielectrical loss (0.025) and high electrical resistance (2.0◌ּ 1010 Ohm◌ּ cm) are characteristic of Elisenvaara syenites which have a high total percentage of microcline and plagioclase (97

Fig. 2. Dependence of dielectric properties on feldspathic rock composition.

for electrical porcelain production in terms of their electrical properties.

**3. Thermal Coefficient of Linear Expansion (ТCLR)** 

estimated using the formula: <sup>0</sup> <sup>6</sup>

α

expansion upon burning of ceramic products.

the TCLR of quartz glass.

Elisenvaara syenites and Kostomuksha volcanics are most efficient feldspathic raw materials

Thermal coefficient of linear expansion (TCLR) is a parameter which shows thermal

TCLR was measured on a DKV- 4 quartz dilatometer on specimens, 55◌ּ × 5 m in size, produced by pressing ground rocks to a grain size of 0.063 mm and subsequent burning in a silitic furnace at 1350°С to reach the maximum density of the specimens. TCLR was

<sup>1</sup> 55,5 10 1 /deg., *<sup>t</sup>*

<sup>−</sup> <sup>−</sup> =× + × <sup>−</sup> where t0 is initial

0 10

*l l ltt*

measurement temperature, 20°С , tl is final measurement temperature, 400, 700°С; l0 is the original length of the specimen, mm, lt is specimen lengthening, mm; 5.5◌ּ (10-6- 1/deg. of

The highest TCLR values (9.15 and 11.75◌ּ 10-6 1/deg., respectively) are characteristic of halleflinta (cake no. 8) at 400º and 700ºC, respectively. Halleflinta differs structurally from pegmatite in having finely dispersed quartz, which contributes to intense dissolution of

mass.%).

quartz in a glass phase. Figure 3 shows that curves 1, 2 and 5 for the cakes of the rocks studied exhibit a non-uniform course of thermal expansion. A rapid increase in TCLR in the range 600 – 700<sup>о</sup> С is typical of compositions with a minimum quartz concentration and high microcline and plagioclase concentrations which form a less viscous liquid phase. Large quantities of quartz in rocks are responsible for the rectilinear course of the TCLR curves (3, 4, 6 and 7). A minimum TCLE value (7.10◌ּ 10-6 1/deg) in the range 600-700<sup>о</sup> С is observed in cake 7 with a minimum quartz concentration (44.0 mass.%), and a maximum TCLR value (8.9◌ּ 10-6 1/deg) in cake 1 with a quartz concentration of 2.5 mass. %.

Fig. 3. Temperature dependence of the thermal coefficient of linear expansion: (numbers as in Table 1).

According to the literature [5] the dependence of TCLR on quartz concentration is due to a difference in the density of minerals. It is known that as mineral density increases, TCLR decreases. As the density of quartz (2.65 g/cm2) is higher than that of albite (2.61 g/cm2) and that of microcline (2.55 g/cm2), low TCLR values in cakes with high quartz concentrations can well be expected. The dependence of TCLR on microcline-plagioclase ratio shows a more complex pattern. As quartz concentration rises with a decline in feldspar concentration [1], also observed in Roza-Lambi quartz porphyry, the porcelain burning expansion interval will expand to 100 <sup>о</sup> С without deformation of products upon burning.

Evaluation of Dielectric Properties from

feldspar from Finland (рН 8.3).

for electrical porcelain production.

1957. P.208-230.

[1] Avgustinnik, А.I. Ceramics. L.: Stroyizdat, 1975. 590 p.

Baltic Shield. Petrozavodsk, 1980. P.108-117.

**5. Conclusions** 

**6. References** 

the Cakes of Feldspathic Raw Material for Electrical Porcelain Production 585

Table 1 shows that suspensions of Khetolambino and Lupikko microcline pegmatites have the highest рН values: 9.67 and 9.82, respectively. Potassic halleflinta, a nonconventional type of feldspathic raw material, has a high рН (10.0). Comparison of the рН of quartzfeldspathic rock suspensions has shown that large quantities of quartz (рН of quartz is 6.4-

Figure 4 shows that rocks that contain a total microcline and plagioclase concentration of 75.8–78.0 mass. % and quartz concentration of 22.0–24.2 mass. % have the highest pH.

Thus, the рН of feldspar suspensions depends on total microcline and plagioclase concentrations and quartz concentration in the rock. The pH of Elisenvaara syenite is 8.25 is consistent with feldspathic raw material according to GOST 21119.3-91 (рН 6-9) and Kemio

The electrical properties ε , lg ρ, tg δ of the cakes of nonconventional types of feldspathic rocks and conventional types, such as pegmatite, are basically affected by alkaline oxides and quartz. Dielectrical permeability depends more on microcline and quartz concentrations in rocks. The angle tangent of dielectrical loss and electrical resistance depend on total microcline and plagioclase concentration. Elisenvaara syenites, which contain high microcline and plagioclase concentrations (97 mass.%), typically show lower tg δ values (0.025) and higher electrical resistance (2.0◌ּ 10-12 Ohm◌ּ cm) than other rocks. Their TCLR is consistent with that of microcline pegmatite. The рН of the suspensions of nonconventional feldspathic raw material depends on total microcline and plagioclase concentration and quartz concentration. Elisenvaara alkaline syenites are a promising feldspathic raw material

[2] Avgustinnik, А.I., Kholodok, N.I, Golod, M.I. et al. On the thermal-physical properties of

[3] Ilyina, V.P. Technological evaluation of feldspathic rocks from the Louhi district //

[5] Kholodok, N.I., Golod, М.I., Popova, I.А., Klabukov, B.N. On the dielectrical

[6] Karyukina, V.N. Determination of minerals from the рН of their suspension // Modern

characteristics of their host environment. L., "Наука",1975. P. 47-49.

and the Kola Peninsula. Petrozavodsk, 1977. P.160-164.

feldspathic minerals from pegmatite veins. // Geophysical study of the eastern

Geological and technological evaluation of minerals and rocks from the Republic of Karelia and some regions of the European continent. Petrozavodsk, 1997. P.57-59. [4] Golod, M.I., Grodnitsky, L.L., Klabukov, B.N. On the dielectrical permeability of

plagioclase from pegmatite veins of the Kola Peninsula// Indicator minerals of the

permeability of potassic feldspars from pegmatite veins // Pegmatites from Karelia

methods for mineralogical study of rocks, ores and minerals. М.: Gosgeotekhizdat,

6.9) decrease their рН considerably, as in Roza-Lambi volcanics (рН 7.1).

Quartz has thus been shown to decrease the TCLR of feldspathic rocks, as indicated by the absence of rapid changes in the curves (Fig.3) in the range 600 – 700 <sup>о</sup> С. High concentrations of feldspathic minerals (microcline, plagioclase - 95 – 97.5 mass. %), which form a less viscous glass phase, increase the TCLR of feldspathic rocks.
