Specific Heat of Amorphous and Crystalline PbTiO3 at Low Temperatures

Specific heat data are reported, 1.7–30 K, on four samples of PbTiO 3 : amorphous ribbon (∼20 vm thick); crystallized ribbon (∼1 µm grain size); crystalline powder (∼1 µm grain size); and ceramic pellet (∼2 µm grain size). Both the amorphous and crystallized ribbon samples display strong Schottky behavior below 4 K with nearly identical (two level) energy separations \({}78\) mK. PbO loss from the thin ribbons is postulated to explain these effects. Below 3 K, the powder and pellet samples display a glasslike linear term in the specific heat, and the coefficients of these terms (1.4×10 -5 J cm -3 K -2 ) are the same magnitude as those found in glasses. All crystalline forms of PbTiO 3 display maxima in C / T 3 at 15 K, and these maxima are accurately represented by single Einstein terms with frequencies 47–52 cm -1 . Amorphous PbTiO 3 displays a C / T 3 maximum at 10 K, as does vitreous SiO 2 . A Debye temperature for crystalline PbTiO 3 of 337 K is reported; the effective Debye temperature for amorphous PbTiO 3 is found to be 256 K.