St Andrews Research Repository

St Andrews University Home
View Item 
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  • Login
JavaScript is disabled for your browser. Some features of this site may not work without it.

Doped alkaline earth (nitride) hydrides

Thumbnail
View/Open
Maarten C. Verbraeken PhD thesis.PDF (3.546Mb)
Date
26/06/2009
Author
Verbraeken, Maarten Christiaan
Supervisor
Irvine, John T. S.
Keywords
Alkaline earth hydride
Alkaline earth nitride hydride
Powder diffraction
Thermal analysis
AC conductivity
Metadata
Show full item record
Altmetrics Handle Statistics
Abstract
The work in this thesis relates to the preparation and structural and electrical characterisation of calcium and strontium hydrides, imides and nitride hydrides. Conventional solid state methods in controlled atmospheres were used to synthesise these materials. High temperature neutron diffraction, thermal analysis and conductivity studies performed on calcium and strontium hydride suggest an order – disorder transition in these materials at 350 – 450°C. Disordering is believed to involve rapid exchange of hydride ions across two crystallographic sites. This manifests itself in a lowering of the activation energy for bulk hydride ion conduction. The hydride ion conduction is good in these undoped materials: σ[total]subscript = 0.01 S/cm for CaH₂ at 1000K; for SrH₂, σ[total]subscript = 0.01 S/cm at 830K. Doping of SrH₂ with NaH causes a significant increase in the low temperature conductivity, due to presence of extrinsic defects. The high temperature conductivity is negatively affected by NaH doping. Calcium nitride hydride (Ca₂NH) was obtained as a single phase material by reacting either calcium metal or calcium hydride (CaH₂) in an argon atmosphere containing 5 – 7% H₂ and 1 – 7% N₂. Imide ions substituting for hydride and nitride ions constitute a major chemical defect in this material. Long range ordering of the nitride and hydride ions occurs, giving rise to a double cubic crystal symmetry. This order breaks down at 600 – 650°C. Applying the same reaction conditions to strontium metal results in a mixed phase of strontium nitride hydride and imide. No long range order in the nitride hydride phase could be observed. Doping Ca₂NH with lithium hydride (LiH) causes the appearance of a second calcium imide phase, whereas doping with sodium hydride (NaH) increases the amount of imide ions as a defect in the nitride hydride structure, thereby decreasing the long range ordering of nitride and hydride ions.
Type
Thesis, PhD Doctor of Philosophy
Collections
  • Chemistry Theses
URI
http://hdl.handle.net/10023/714

Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.

Advanced Search

Browse

All of RepositoryCommunities & CollectionsBy Issue DateNamesTitlesSubjectsClassificationTypeFunderThis CollectionBy Issue DateNamesTitlesSubjectsClassificationTypeFunder

My Account

Login

Open Access

To find out how you can benefit from open access to research, see our library web pages and Open Access blog. For open access help contact: openaccess@st-andrews.ac.uk.

Accessibility

Read our Accessibility statement.

How to submit research papers

The full text of research papers can be submitted to the repository via Pure, the University's research information system. For help see our guide: How to deposit in Pure.

Electronic thesis deposit

Help with deposit.

Repository help

For repository help contact: Digital-Repository@st-andrews.ac.uk.

Give Feedback

Cookie policy

This site may use cookies. Please see Terms and Conditions.

Usage statistics

COUNTER-compliant statistics on downloads from the repository are available from the IRUS-UK Service. Contact us for information.

© University of St Andrews Library

University of St Andrews is a charity registered in Scotland, No SC013532.

  • Facebook
  • Twitter