The possibility of using wollastonite as one of the main components in non-fritted opacified glazes for sanitary ceramics is demonstrated. The main physicochemical properties of synthesized coatings are determined, the specifics of their structure and phase composition are analyzed.A topical problem of ceramic production is the expansion of material resources for the porcelain-faience industry and simultaneous upgrade of product quality. Wollastonite is of great interest in this respect.This raw material is white-colored powder belonging to pyroxenoides made up by [SiO 4 ] tetrahedron chains, whose bases are not in the same plane, even approximately, but are differently oriented in such a way that the chain pattern is repeated after each third tetrahedron. Two modifications of wollastonite are known: a-CaSiO 3 (pseudowollastonite) and b-CaSiO 3 (proper wollastonite), which are closely interrelated [1]. Pseudowollastonite crystallizes in the pseudohexagonal syngony and wollastonite in the triclinic syngony. At a temperature of 1125°C wollastonite is irreversibly transformed into pseudowollastonite with a slight volume alteration. Its melting temperature is 1540°C, the density of a-wollastonite is 3.09´10 3 kg/m 3 , and that of b-wollastonite 2.87´10 3 kg/m 3 . Its Mohs hardness is 4.5 -6.0. The CLTE of a-wollastonite is 118´10 -7 K -1 , and that of b-wollastonite 65´10 -7 K -1 . Wollastonite crystals have a needle-like shape; besides, fibrous and discoid crystals are found as well [2].Analysis of published data [2,3] indicates that wollastonite is most frequently used in the production of construction materials, in particular, in the production of facing tiles. Wollastonite additives range from 15 to 65% (here and elsewhere wt.%) depending on the chemical composition. It is known that wollastonite is used in the production of lowmelting glazes, which makes it possible to lower the frit content to 20% and, accordingly, decrease the cost of the glaze. However, no published data have been found on the use of this component in nonfritted glazes and its effect on the properties of coatings.We have attempted to fill this vacancy in the systematic study of the physicochemical (luster, whiteness, CLTE, microhardness) properties of coatings and to reveal a correlation between the said properties and the compositions of nonfritted glazes for sanitary ware made from porcelain mixtures.For our study we selected wollastonite concentrate VP-25 (hereafter "wollastonite") produced by the TransResurs Company (Russia) according to standard TU 5726-001-50889697-01. The averaged chemical composition of wollastonite is as follows (%): 50.00 SiO 2 , 0.16 Fe 2 O 3 , 45.20 CaO, and 0.61 calcination loss.X-ray phase analysis of wollastonite concentrate indicated that the material mainly includes wollastonite; a-quartz is present in insignificant quantities.Wollastonite concentrate was introduced in an amount of 55% into previously analyzed glazes of series 1, 2, and 3 [3] with zircosil content equal to 10.0, 12.5, and 15.0%, respectively...
