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Phase Transformation during Plasma Spraying of Hydroxyapatite–10‐wt%‐Zirconia Composite Coating
Author(s) -
Chou BangYen,
Chang Edward,
Yao Shyue Yen,
Chen Jen Min
Publication year - 2002
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.1151-2916.2002.tb00147.x
Subject(s) - materials science , zirconium , cubic zirconia , composite number , yttrium , amorphous solid , coating , phase (matter) , transmission electron microscopy , impurity , lattice constant , analytical chemistry (journal) , chemical engineering , ceramic , nuclear chemistry , mineralogy , composite material , crystallography , metallurgy , diffraction , chemistry , nanotechnology , physics , organic chemistry , engineering , chromatography , optics , oxide
This study aims to explore phase transformation in plasma‐sprayed hydroxyapatite (HA) + 10 wt% ZrO 2 –8‐mol%‐Y 2 O 3 composite coating, using separately prepared HA and ZrO 2 –8‐mol%‐Y 2 O 3 coatings as a control. Changes in the phase and chemistry of the coatings are characterized by X‐ray diffractometry, with lattice‐constant measurement (Cohen's method), and by transmission electron microscopy. Experimental results show evidence of diffusion, in the liquid state, of calcium ions from the HA matrix into the ZrO 2 . This behavior causes the formation of the following structural features in the composite coating: (i) a CaO‐doped ZrO 2 solid solution (ZrO 2 –7.7 mol% Y 2 O 3 –4.4 mol% CaO); (ii) a mixture of ZrO 2 and CaZrO 3 having a crystal‐orientation relationship; (iii) an amorphous phase containing elements of calcium, phosphorus, zirconium, and yttrium; and (iv) a remaining CaO‐poor HA matrix (Ca 10− x (HPO 4 ) x (PO 4 ) 6− x (OH) 2− x ; x = 0.06). Rationales for the greatly decreased impurity phases of CaO and Ca 4 P 2 O 9 found in the composite coating are discussed.