TY - JOUR

T1 - Crystalline borosilicates of alkali and alkaline earth metals: hierarchy, fundamental building blocks and thermal expansion

AU - Krzhizhanovskaya, Maria G.

AU - Bubnova, Rimma S.

AU - Filatov, Stanislav K.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - A brief review is presented of the structure hierarchy, main fundamental building blocks (FBBs) and some thermal characteristics of crystalline alkali and alkaline earth borosilicates. Low-dimensional borosilicate anions are typical for borosilicates with considerable contents of non-tetrahedrally coordinated cations. There are only six types of borosilicate anions containing boron in BO3 triangles, which are almost never connected to silicon tetrahedra. The lower the ratio "non-tetrahedral/tetrahedral cation", the higher the dimension of the layered and framework anions that form. Most Si-dominant borosilicates (B/Si=1) with a low content of non-tetrahedrally coordinated cations have 3D-framework structures formed by boron and silicon atoms in tetrahedral coordination only. As with aluminosilicates, 3D-borosilicate structures contain a great variety of rings of tetrahedra, which are the main FBBs of borosilicate structures. The most common rings of tetrahedra are 4-, 6-and 8-membered. An ordered distribution of Si and B is typical for borosilicates. There are many OH-containing borosilicates, especially among the structures with 0D-, 1D-and 2D-anions; conversely, they almost never have H 2O molecules in the crystal structure. OH-groups are often involved in the coordination of boron. Non-tetrahedral alkali and alkaline earth cations are coordinated by oxygen or hydroxyl groups with usual coordination numbers: lithium is 4-coordinated, sodium is mostly 6-coordinated, and 8-coordination is typical for calcium. Other large cations have irregular coordinations with more than eight oxygen atoms. Thermal expansion coefcients (TECs) determined for 31 natural and synthetic compounds have relatively low values independent of the dimensionality of the structure. The linear TECs of crystals are slightly higher than those of glasses of corresponding composition; the average values are 10×10 -6 and 8×10- 6°C -1 for crystals and glasses, respectively.

AB - A brief review is presented of the structure hierarchy, main fundamental building blocks (FBBs) and some thermal characteristics of crystalline alkali and alkaline earth borosilicates. Low-dimensional borosilicate anions are typical for borosilicates with considerable contents of non-tetrahedrally coordinated cations. There are only six types of borosilicate anions containing boron in BO3 triangles, which are almost never connected to silicon tetrahedra. The lower the ratio "non-tetrahedral/tetrahedral cation", the higher the dimension of the layered and framework anions that form. Most Si-dominant borosilicates (B/Si=1) with a low content of non-tetrahedrally coordinated cations have 3D-framework structures formed by boron and silicon atoms in tetrahedral coordination only. As with aluminosilicates, 3D-borosilicate structures contain a great variety of rings of tetrahedra, which are the main FBBs of borosilicate structures. The most common rings of tetrahedra are 4-, 6-and 8-membered. An ordered distribution of Si and B is typical for borosilicates. There are many OH-containing borosilicates, especially among the structures with 0D-, 1D-and 2D-anions; conversely, they almost never have H 2O molecules in the crystal structure. OH-groups are often involved in the coordination of boron. Non-tetrahedral alkali and alkaline earth cations are coordinated by oxygen or hydroxyl groups with usual coordination numbers: lithium is 4-coordinated, sodium is mostly 6-coordinated, and 8-coordination is typical for calcium. Other large cations have irregular coordinations with more than eight oxygen atoms. Thermal expansion coefcients (TECs) determined for 31 natural and synthetic compounds have relatively low values independent of the dimensionality of the structure. The linear TECs of crystals are slightly higher than those of glasses of corresponding composition; the average values are 10×10 -6 and 8×10- 6°C -1 for crystals and glasses, respectively.

UR - http://www.scopus.com/inward/record.url?scp=85072329110&partnerID=8YFLogxK

U2 - 10.13036/17533562.60.4.049

DO - 10.13036/17533562.60.4.049

M3 - Обзорная статья

VL - 60

SP - 129

EP - 139

JO - European journal of glass science and technology. Part B, Physics and chemistry of glasses

JF - European journal of glass science and technology. Part B, Physics and chemistry of glasses

SN - 1753-3562

IS - 4

ER -