Lamination of magnesium oxide spacers to barium strontium zirconium titanate ceramics

We propose an innovative idea to bond the dielectric barium strontium zirconium titanate (BSTZO) plates with magnesium oxide (MgO) as the spacers to achieve a hermetic module without any air gaps between the dielectric and the spacer. The gold metallization can be applied across the whole assembly to create an integrated electrode. The gold metallization also eliminates pressure contact by external copper plates assemblies, which are required to achieve good contacts between the copper plates and the metallized surfaces of the BSTZO. The MgO spacers are processed using a dry-pressing and pressureless-sintering method. The thermal expansion coefficient (CTE) of BSTZO and MgO spacer was measured. In addition to matching the CTE between BSTZO dielectric and the MgO spacer, it is also critical to develop a good bonding material with CTE matching to BSTZO and MgO spacer. The effect of CTE for various bonding compositions on the dielectric properties was thoroughly studied and reported. The mechanism explaining the high and low dielectric constants for the laminates is proposed and discussed based on the CTE results and their effect on microstructural development.