Dynamics of ion transport and charge compensation in thermally poled glasses
Restricted (Penn State Only)
- Author:
- Nieves Sanabria, Cesar
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 14, 2022
- Committee Members:
- Michael Lanagan, Chair & Dissertation Advisor
Suzanne Mohney, Major Field Member
John Mauro, Program Head/Chair
Seong Kim, Outside Unit & Field Member
John Mauro, Major Field Member - Keywords:
- glass
ion migration
thermal poling
tsdc
comsol
dielectric breakdown
acid leaching
polymer coating
electrical properties - Abstract:
- Due to their high breakdown strength and high energy density, glasses are promising dielectric materials for a wide range of cutting-edge technologies. For many applications and during manufacturing processes, network modifiers are introduced to the glass network structure, altering the glass properties. For example, it is well known that the nature and concentration of the network modifiers and glass structure affect electrical conduction glasses. The application of an electric field and temperature also affect electrical conduction. However, there are to this point some unanswered questions regarding this subject. Therefore, the focus of the study is to understand ionic transport and charge compensation mechanisms and their effect on electrical conduction and breakdown phenomena. Electrical conduction was studied in soda-lime-silica (SLS), and D263T (an alkali boroaluminosilicate) by electrochemical impedance spectroscopy and thermally stimulated depolarization current measurements. These glasses were chosen due to their high alkali content, which made them an excellent candidate for detailed exploration on charge transport behavior. This study demonstrated that Na+ migration governs leakage current in these glasses with a more prominent effect in SLS due to its high Na content and lower activation energy for Na transport than D263T. Additionally, the contribution of protons to compensate for the intensified field caused by the formation of a Na-depleted region was observed in D263T. A 2D COMSOL model was implemented to evaluate the electric field distribution due to the migration of Na+ ions and proton injection as a charge compensation mechanism. The simulations agreed with the experimental observations confirming the presence of protons in D263T. To further investigate the implications of protons to ionic transport, an acid leaching treatment was conducted in SLS to remove the Na from the glass surface and replace them with protons. The study demonstrated that the acid leaching treatment causes surface modifications affecting the migration of Na+ ions and promoting proton conduction. Dielectric breakdown measurements were conducted in D263T and AF32 (an “alkali-free boroaluminosilicate). These glasses were chosen in this study for their thickness (30μm) and their lower and high values in the alkali content. It was demonstrated that the breakdown in D263T was primarily controlled edge electrode failures caused by intensified local field leading, which resulted from local inhomogeneity in the system. In AF32, the breakdown events were generally caused by electrical discharges and thermal shock, causing cracking. Implementing a polymer coating caused these breakdown features to be shifted to higher breakdown voltages and longer times. The polymer coating mitigated intensified electric field and reduced the risk of surface damage.