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Formation of Alkoxy‐Derived lead Niobates in the PbO‐Rich Region
Author(s) -
Yamaguchi Osamu,
Mukaida Yasumichi
Publication year - 1990
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1990.tb09816.x
Subject(s) - monoclinic crystal system , tetragonal crystal system , materials science , amorphous solid , crystallography , trigonal crystal system , niobium , alkoxy group , mineralogy , crystal structure , chemistry , metallurgy , organic chemistry , alkyl
The formation of lead niobates in the PbO‐rich region is studied using powders prepared by the simultaneous hydrolysis of lead and niobium alkoxides. Cubic 3PbO·2Nb 2P O 5 solid solutions crystallize at low temperatures from amorphous materials having concentrations of 58 to 75 mol% PbO. The lattice parameter a increases linearly from 1.0544 to 1.0708 nm with increasing PbO. At higher temperatures the solid solutions made with 66.67 and 71.43 mol% PbO transform into 2PbO·Nb 2 O 5 (monoclinic) and 5PbO·2Nb 2 O s (monoclinic), respectively. Monoclinic 5PbO·2Nb 2 O 5 transforms into a new modification at = 3850° to = 3900°C. It has a rhombohedral unit cell with a = 0.7461 nm and c = 4.8092 nm ( a = 1.6599 nm, a = 25.97°). In the presence of excess lead, monoclinic 5PbO·2Nb 2 O 5 transforms into tetragonal 3PbO·Nb 2 O 5 .