Titre du document / Document title

Thermal behavior of larderellite, NH₄[B₅O₇(OH)₂]H₂O

Auteur(s) / Author(s)

ANDERSON Yu. E. ; BUBNOVA R. S. ; FILATOV S. K. ; POLYAKOVA I. G. ; KRZHIZHANOVSKAYA M. G. ;

Résumé / Abstract

Thermal behavior of larderellite, NH₄[B₅O₇(OH)₂].H₂O, was studied by high-temperature X-ray diffraction (HTXRD), DTA and TG methods. It has been revealed that resulting the dehydration of larderellite there appeared two unknown phases: I and II. Presumably, they correspond: phase-I to NH₄[B₅O₇(OH)₂], and phase-II - to NH₄B₅O₈. According to HTXRD the sequence of phase transitions corresponds to the DTA and TG data: weight losses in three steps on the TG curve and three big endothermic effects on the DTA curve. Studied for the first time, thermal expansion of larderellite is the sharply anisotropic one, α₁₁ = 32, α₂₂ = 53, α₃₃ = -3, α_V = 82.10^-6 °C^-1, (cΛα₃₃) angle = 53°. Maximum thermal expansion is along b axis, i. e. along zig-zag chains of the pentaborate groups, that may evidence their straightening under heating.

Revue / Journal Title

Zapiski Vserossijskogo mineralogičeskogo obŝestva   ISSN 0869-6055 

Source / Source

2005, vol. 134, n^o1, pp. 103-113 [11 page(s) (article)]

Langue / Language

Russe

Editeur / Publisher

Nauka, Sankt-Peterburg, RUSSIE, FEDERATION DE  (1992) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 4673, 35400013476214.0110