Syntheses and crystal structures of the. alpha. - and. beta. -forms of the orthoborate Sr sub 2 Cu(BO sub 3 ) sub 2

Journal Article · Tue Aug 01 04:00:00 EDT 1989 · Journal of Solid State Chemistry; (USA)

DOI:https://doi.org/10.1016/0022-4596(89)90019-4· OSTI ID:7156686

Smith, R W; Keszler, D A ^[1]

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1. Oregon State Univ., Corvallis (USA)

The low-temperature {alpha}-form and the high-temperature {beta}-form of the compound of formula Sr{sub 2}Cu (BO{sub 3}){sub 2} have been synthesized and their structures established by single-crystal X-ray methods. The {alpha}-phase crystallizes in a monoclinic cell of dimensions a = 5.707(1), b = 8.796(2), c = 6.027(1) {angstrom}, and {beta} = 116.98(1){degree} with Z = 2; the space group is P2{sub 1}/c. The structure was determined from 1039 independent reflections and refined to the final residuals R = 0.037 and R{sub w} = 0.051. It is composed of sheets of isolated CuO{sub 4} square planes that are rotated out of the b-c plane and connected by BO{sub 3} and SrO{sub 7} units; it is isomorphous to the compound Na{sub 2}Cu(CO{sub 3}){sub 2}. The {beta}-phase crystallizes in an orthorhombic cell of dimensions a = 7.612(3), b = 10.854(7), c = 13.503(4) {angstrom} with Z = 8; the space group is Pnma. The structure was determined from 1235 independent reflections and refined to the final residuals R = 0.030 and R{sub w} = 0.039. This structure exhibits isolated units of stoichiometry Cu{sub 2}(BO{sub 3}){sub 4} that are built from CuO{sub 4} distorted square planes and triangular BO{sub 3} groups. These units are bridged by three crystallographically independent Sr atoms. The phase transition from the {alpha}-phase to the {beta}-phase occurs at 800{degree}C. Considerable bond scission and reformation between two phases indicate that the transition is first order.

• OSTI ID: 7156686
• Journal Information: Journal of Solid State Chemistry; (USA), Journal Name: Journal of Solid State Chemistry; (USA) Vol. 81:2; ISSN JSSCB; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360000* -- Materials
360100 -- Metals & Alloys
360102 -- Metals & Alloys-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
BORIDES
BORON COMPOUNDS
COPPER
CRYSTALS
DATA
DATA ANALYSIS
ELEMENTS
EXPERIMENTAL DATA
HIGH TEMPERATURE
INFORMATION
LOW TEMPERATURE
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
NONMETALS
NUMERICAL DATA
OXYGEN
PHASE STUDIES
STRONTIUM BORIDES
STRONTIUM COMPOUNDS
SYNTHESIS
TRANSITION ELEMENTS