High-temperature crystal chemistry of layered calcium borosilicates: CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (‘bakerite’) and Ca2B2SiO7 (synthetic analogue of okayamalite)

Результат исследований: Научные публикации в периодических изданияхстатья

2 Цитирования (Scopus)

Выдержка

The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30–900 °C for natural samples of datolite, CaBSiO4(OH), and ‘bakerite’, Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °С. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30–500 °C, datolite and ‘bakerite’ demonstrate very similar and relatively low volumetric thermal expansion: αv = 29 and 27 × 10−6 °C−1, respectively. A high thermal expansion anisotropy (αmaxmin ~ 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the (a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, Rwp = 6.61, RBragg = 2.68%].

Язык оригиналаанглийский
Страницы (с-по)463-473
Число страниц11
ЖурналPhysics and Chemistry of Minerals
Том45
Номер выпуска5
DOI
СостояниеОпубликовано - 1 мая 2018

Отпечаток

Crystal chemistry
crystal chemistry
Calcium
calcium
wollastonite
thermal expansion
Temperature
crystal structure
X-ray diffraction
Thermal expansion
cristobalite
thermogravimetry
Crystal structure
calorimetry
X ray diffraction
diffraction
topology
symmetry
Crystal symmetry
anisotropy

Предметные области Scopus

  • Материаловедение (все)
  • Геохимия и петрология

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title = "High-temperature crystal chemistry of layered calcium borosilicates: CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (‘bakerite’) and Ca2B2SiO7 (synthetic analogue of okayamalite)",
abstract = "The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30–900 °C for natural samples of datolite, CaBSiO4(OH), and ‘bakerite’, Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °С. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30–500 °C, datolite and ‘bakerite’ demonstrate very similar and relatively low volumetric thermal expansion: αv = 29 and 27 × 10−6 °C−1, respectively. A high thermal expansion anisotropy (αmax/αmin ~ 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the (a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) {\AA}, V = 256.76(3) {\AA}3, Rwp = 6.61, RBragg = 2.68{\%}].",
keywords = "Bakerite, Calcium borosilicate, Crystal structure, Datolite, High-temperature X-ray diffraction, Okayamalite, Phase transition, Thermal expansion",
author = "Krzhizhanovskaya, {Maria G.} and Gorelova, {L. A.} and Bubnova, {R. S.} and Pekov, {I. V.} and Krivovichev, {S. V.}",
year = "2018",
month = "5",
day = "1",
doi = "10.1007/s00269-017-0933-y",
language = "English",
volume = "45",
pages = "463--473",
journal = "Physics and Chemistry of Minerals",
issn = "0342-1791",
publisher = "Springer",
number = "5",

}

High-temperature crystal chemistry of layered calcium borosilicates : CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (‘bakerite’) and Ca2B2SiO7 (synthetic analogue of okayamalite). / Krzhizhanovskaya, Maria G.; Gorelova, L. A.; Bubnova, R. S.; Pekov, I. V.; Krivovichev, S. V.

В: Physics and Chemistry of Minerals, Том 45, № 5, 01.05.2018, стр. 463-473.

Результат исследований: Научные публикации в периодических изданияхстатья

TY - JOUR

T1 - High-temperature crystal chemistry of layered calcium borosilicates

T2 - CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (‘bakerite’) and Ca2B2SiO7 (synthetic analogue of okayamalite)

AU - Krzhizhanovskaya, Maria G.

AU - Gorelova, L. A.

AU - Bubnova, R. S.

AU - Pekov, I. V.

AU - Krivovichev, S. V.

PY - 2018/5/1

Y1 - 2018/5/1

N2 - The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30–900 °C for natural samples of datolite, CaBSiO4(OH), and ‘bakerite’, Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °С. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30–500 °C, datolite and ‘bakerite’ demonstrate very similar and relatively low volumetric thermal expansion: αv = 29 and 27 × 10−6 °C−1, respectively. A high thermal expansion anisotropy (αmax/αmin ~ 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the (a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, Rwp = 6.61, RBragg = 2.68%].

AB - The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30–900 °C for natural samples of datolite, CaBSiO4(OH), and ‘bakerite’, Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °С. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30–500 °C, datolite and ‘bakerite’ demonstrate very similar and relatively low volumetric thermal expansion: αv = 29 and 27 × 10−6 °C−1, respectively. A high thermal expansion anisotropy (αmax/αmin ~ 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the (a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, Rwp = 6.61, RBragg = 2.68%].

KW - Bakerite

KW - Calcium borosilicate

KW - Crystal structure

KW - Datolite

KW - High-temperature X-ray diffraction

KW - Okayamalite

KW - Phase transition

KW - Thermal expansion

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U2 - 10.1007/s00269-017-0933-y

DO - 10.1007/s00269-017-0933-y

M3 - Article

AN - SCOPUS:85035804617

VL - 45

SP - 463

EP - 473

JO - Physics and Chemistry of Minerals

JF - Physics and Chemistry of Minerals

SN - 0342-1791

IS - 5

ER -