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Hydrothermal Synthesis of Single Crystalline (K,Na)NbO 3 Powders
Author(s) -
Sun Ce,
Xing Xianran,
Chen Jun,
Deng Jinxia,
Li Lu,
Yu Ranbo,
Qiao Lijie,
Liu Guirong
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200601131
Subject(s) - orthorhombic crystal system , natural bond orbital , monoclinic crystal system , crystallography , chemistry , hydrothermal synthesis , hydrothermal circulation , phase (matter) , phase boundary , crystal structure , powder diffraction , mineralogy , chemical engineering , organic chemistry , engineering , molecule
(K 1– x Na x )NbO 3 ( x = 0.01, 0.24, 0.89, 0.91, 0.99) single crystalline powders with perovskite structure were synthesized by a hydrothermal method with Nb 2 O 5 in a mixed solution of KOH and NaOH at 220 °C for 24 h. XRD investigations showed that the structure of the synthesized (K 1– x Na x )NbO 3 ceramics changed from a KNbO 3 ‐type orthorhombic phase (space group Bmm 2) to a NaNbO 3 ‐type monoclinic phase (space group Pm ) with the increase of Na content. The present results confirmed that (K 1– x Na x )NbO 3 exhibited a morphotropic phase boundary (MPB) at around 50 %K separating the orthorhombic phase and monoclinic phase. FE‐SEM images showed that the morphological structures of niobates were cubes and nanofingers. The TEM image and the selected area electron diffraction pattern of (K 0.01 Na 0.99 )NbO 3 showed the as‐synthesized powder was single crystalline and indexed to be monoclinic. The phase evolution of the products in the hydrothermal route revealed that the hydrothermal synthesis of (K 1– x Na x )NbO 3 underwent two steps, where an intermediate product (K 8–8 x Na 8 x )Nb 6 O 19 · n H 2 O was found in the early stage and then pure (K 1– x Na x )NbO 3 was obtained after another 30 min of hydrothermal treatment.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)