You can use silver diffusion bonding developed by Los Alamos National Lab.
It can be done at atmospheric pressure with silver sputtered pieces, T >
150C and applying pressure in the order of several thousand PSI depending
on your sample.

Low viscosity epoxy from Hysol also results in bondlines in the order of
microns.

Levent

 On Wed, 30 Sep 1998, Phil Rayner wrote:

> Hello everybody,
>
> I'm building a piezo micro motor, and I'm looking for methods of bonding bulk
> PZT to a stainless steel or silicon substrate.
> These can then be lapped/ precision ground down to required thickness (30um
> or so), giving much better propeties than thin or thick film PZTs, which we
also
> do here.
> Does anybody have any experience of bonding wafers with gold-silicon (or
> another type of) diffusion bonding, sputtering solder layers down or using a
sol-
> gel intermediate layer.
> Really, I'm looking for a way to avoid epoxy bonding (which could end up
giving
> a bond as thick as the PZT), so all ideas will be very much appreciated.
>
> Thanking you in advance
>
> Phil Rayner
>
>