I am grateful to the organisers, and fellow students,
of the HERCULES 1992 course for a most exhilirating and memorable
introduction to the world of x-ray diffraction; and to the
participants of the 1993 Errice workshop on high-T
superconductors
for discussions which motivated much of the work in this thesis.
I gratefully acknowledge the help of a number of people who have collaborated with this work; without the cyrstals they supplied the work could never have been undertaken: Shamina Chowdhury at Oxford (who also carried out the invaluable compositional analysis in Chapter 5); Gerta Balakrishnan and Jason Gardener at Warwick (who carried out some annelaing treatments); Alison Marshall at Birmingham; and Y.F. Yan and Z.X. Zhao at Beijing. Stewart Clark kindly aided the conversion of the simulation program in Chapter 7 to the Connection Machine. My thanks also go to Hugh Vass for his patient and expert technical assistance; he drew upon some mystical senses to keep the GX21 up and the x-rays flowing. Some of the results of the collaborations have been published (they form parts of Chapters 3 and 6) and are included in Appendix B.
Finally, many thanks are due to: Peter Hatton for giving me the opportunity, the encouragement, and always the space I needed to get on and write this thing; to all my friends for the many happy distractions they've provided; and especially to Marcie for keeping my writing (and myself) in a fit state; and to my parents for everything, this is dedicated to them.