DSM conducted four rounds of cryogenic testing on piezo-ceramic (PZT) stacks. The tests were completed as part of ongoing piezo actuation system product development efforts for DSM’s Small Business Innovative Research (SBIR) programs. The test plan and results are available for purchase for $950. The PZT vendors are not identified in the report.
Many PZT fabricators claim that multilayer stacks can be used at cryogenic temperatures. DSM tested multiple vendor’s PZT stacks under varying cryogenic conditions. Driving the stacks with relatively high frequency oscillations appears to be particularly harmful. In order to offer piezo-actuators and piezo-motors that can operate at very low temperature, DSM has been investigating combinations of stack construction, lead attachment technique, and coating that will demonstrate reliable operation from room temperature down to cryogenic temperature.
During Round 1 of cryogenic stack testing, two types of stacks were tested. 20 from “X-ceramic” and 20 from “Y-ceramic”. Test 1 consisted of 1 thermal cycle, holding a temperature of less than 100 K,1,000,000 actuations, and a low power waveform (20 Hz sine wave). All of the stacks survived this test. “Y-ceramic” thick-coated samples showed the beginnings of cracks after Test 1. Test 2 consisted of 100 thermal cycles from 100 K to 300 K. There were no actuations or waveforms. “Y-ceramic” stacks with thick coatings showed signs of failure. “Y-ceramic” stacks with thin coatings were successful. “X-ceramic” stacks with thin coating were also successful. Test 3 consisted of 1 thermal cycle at less than 110 K. There were 1,000,000 actuations and a high power waveform (600 Hz pseudo sine wave). All “Y-ceramic”type stacks had failures. These stacks were removed from testing. Test 4 consisted of 100 thermal cycles from 100 K to 300 K. The actuations were continuous with a high power waveform. No ceramic material survived beyond 26 thermal cycles. This test ended early.
Round 2 tested 8 “X-ceramic” stacks. The primary objective of this round of testing was to test the perpendicular lead connection reliability of the black coated “X-ceramic” stacks. Test 1 consisted of 50 thermal cycles from 100 K to 300 K with continuous actuations at low power (5 Hz sine wave). All coated stacks survived and 2 uncoated stacks failed at 42 thermal cycles. Test 2 consisted of the same thermal cycles but had continuous actuation with high power waveforms (600 Hz pseudo sine wave). 2 “X-ceramic” stacks failed after 12 cycles. This test ended early.
Round 3 tested three types of “X-ceramic” stacks and “Z-ceramic”stacks. Test 1 had 50 thermal cycles from 100 – 300 K. There were 20,000 actuations at about 300 K and 100 K only with high power waveforms. All “X-ceramic”stacks failed with high voltage, custom coated, manufacturer cryo coated. All “Z-ceramic”stacks survived. Test 2 held the stacks at < 100 K for 2,000,000 actuations at high power. All “Z-ceramic” stacks survived. Test 3 had 50 thermal cycles from 100 – 300 K with continuous high power actuations. All “Z-ceramic” stacks survived.
Round 4 tested 20 “Z-ceramic” stacks. Test 1 held the stacks at approximately 300 Kelvin for 1,000,000 low power actuations (20 Hz sine wave). All stacks survived. Test 2 held the stacks at <110 K for 1,000,000 high power (600 Hz pseudo sine wave) actuations. All stacks survived. Test 3 had 50 thermal cycles from 110 – 300 Kelvin with continuous high power actuations. All stacks survived this test as well.