TY - JOUR
T1 - Crystal chemistry on a lattice
T2 - The case of BZN and BZN-related pyrochlores
AU - Liu, Yun
AU - Withers, Ray L.
AU - Welberry, T. R.
AU - Wang, Hong
AU - Du, Huiling
PY - 2006/7
Y1 - 2006/7
N2 - This paper uses a diagnostic, highly structured diffuse intensity distribution to investigate the local crystal chemistry of (Bi1.5Zn0.5-δ)(Zn0.5Nb1.5)O7-δ (BZN) as well as Sn4+ and Ti4+, B site substituted, BZN-related pyrochlore phases. The structured diffuse distribution of the B site substituted material is found to be remarkably similar to that observed for BZN itself. In the special case of (Bi1.5Zn0.5)(Ti1.5Nb0.5)O7 (BZNT), the continuous G±〈10l〉* type diffuse streaking characteristic of BZN-related pyrochlores has virtually condensed out to give just G±〈001〉* "satellite reflections" and a P-centred, close to a superstructure phase of average pyrochlore unit cell dimensions. Bond valence sum considerations are used to investigate the local crystal chemistry of this BZNT phase and to derive a plausible model for this superstructure phase. Monte Carlo modelling is used to confirm the plausibility of the model proposed. The underlying crystal chemistry of BZN and BZN-related pyrochlores is shown to result from strong local Bi/Zn ordering rules and associated large amplitude structural relaxation.
AB - This paper uses a diagnostic, highly structured diffuse intensity distribution to investigate the local crystal chemistry of (Bi1.5Zn0.5-δ)(Zn0.5Nb1.5)O7-δ (BZN) as well as Sn4+ and Ti4+, B site substituted, BZN-related pyrochlore phases. The structured diffuse distribution of the B site substituted material is found to be remarkably similar to that observed for BZN itself. In the special case of (Bi1.5Zn0.5)(Ti1.5Nb0.5)O7 (BZNT), the continuous G±〈10l〉* type diffuse streaking characteristic of BZN-related pyrochlores has virtually condensed out to give just G±〈001〉* "satellite reflections" and a P-centred, close to a superstructure phase of average pyrochlore unit cell dimensions. Bond valence sum considerations are used to investigate the local crystal chemistry of this BZNT phase and to derive a plausible model for this superstructure phase. Monte Carlo modelling is used to confirm the plausibility of the model proposed. The underlying crystal chemistry of BZN and BZN-related pyrochlores is shown to result from strong local Bi/Zn ordering rules and associated large amplitude structural relaxation.
KW - BZN-related pyrochlores
KW - Crystal chemistry
KW - Electron diffraction study
KW - Structured diffuse distribution
KW - Superstructure phase
KW - Zincanyl structural units
UR - http://www.scopus.com/inward/record.url?scp=33744995036&partnerID=8YFLogxK
U2 - 10.1016/j.jssc.2006.04.017
DO - 10.1016/j.jssc.2006.04.017
M3 - Article
SN - 0022-4596
VL - 179
SP - 2141
EP - 2149
JO - Journal of Solid State Chemistry
JF - Journal of Solid State Chemistry
IS - 7
ER -