Re: Quartz Crystal ESR vs Temperature

On Sun, 18 May 2008 12:31:45 -0700 (PDT), whit3rd <whit3rd@xxxxxxxxx>
wrote:

On May 16, 10:32 am, Jeff Liebermann <je...@xxxxxxxxxx> wrote:
On Fri, 16 May 2008 08:07:00 -0700, Mike <M...@xxxxxxxxxxxxxxx> wrote:
Crystal data sheets generally just give a maximum ESR value. I'm
interested in how ESR changes over temperature ...

I vaguely recall (from 30 years ago) doing temperature runs of various
crystals in a fixture.  While we were primarily interested in their
frequency versus temp characteristic, I also recorded the series
resistance.  The series resistance varied wildly over the production
lots received from the vendors, but each crystal was fairly stable
over temperature.  I vaguely recall that it was almost linear, with a
slight decrease in series resistance with increasing temperature.

The normal quartz processing includes some water-cooled
grinding and polishing;

We didn't use water cooling or grinding and never got involved in the
growing or slicing part. The blanks were supplied slightly low in
frequency by the vendor. We used an SS White abrasive sand blaster to
do the tuning. If too much was blasted off, elecroless silver was
sprayed onto the contact plating to move it down in frequency. It was
a manual process controlled by an operator manipulating a Morse code
paddle. Tap to the left, and it sand blasts. Tap to the right, and
it adding plating. It took considerable expertise and practice to get
it right. The blank was anything but stable during this process and
would frequently overshooting in both directions. The operator had to
predict where the counter would eventually stop. The last tuning step
was to blow off any residual crud from the surface with a compressed
air blast. We tried various solvent baths and found that an air blast
was good enough.

it turns out that OH radical contamination
can dominate the internal losses. The effect, as I recall,
is minimized at elevated temperature (80 C or so?).
I dimly remember Hughes corporation was involved in making
artificial quartz crystals, and found that growth
in water caused the artificial quartz to be inferior to natural.
Alas, this was 20 years ago, it'd take a search for 'alpha SiO2'
in a good library to find a reference.
--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.