LOW-TEMPERATURE THERMAL-CONDUCTIVITY, HEAT-CAPACITY, AND HEAT-GENERATION OF PZT

The thermal conductivity, heat capacity and heat generation properties of two poled piezoceramic materials, a ''soft'' PZT-5H and a ''hard'' PZT-4S, were measured over the temperature range from 20 K to above 1 50 K. A single sample was used for each test type. The thermal conduct ivity (in the poling direction) of PZT-SH increased from 0.010 W/m-K a t 15 K to 0.14 W/m-K at 300 K. The thermal conductivity of PZT-48 was generally higher, increasing from 0.018 to 3.34 W/m-K over the same te mperature range. The heat capacity of PZT-5H increased from 23.3 J/kg- K at 23 K to 348 J/kg-K at 153 K, while the heat capacity of PZT-48 in creased from 42.6 to 159 J/kg-K over the same range. Heat generation v aried with drive amplitude and frequency as well as temperature, and i s presented as an effective dielectric loss property. The dielectric l oss for PZT-5H at 100 Hz varied from 4.15 (20 K) to 23.1 (150 K), and at 2000 Hz from 9.8 (20K) to 26.5 (150 K). As expected, the dielectric loss for the ''hard'' PZT-4S was lower, and varied at 100 Hz from 2.8 6 (25 K) to 16.2 (150 K), and at 2000 Hz from 6.47 (25 K) to 20.2 (150 K). A ''transition'' type behavior between 50 K and 80 K was observed for both materials.