Influence of moisture on pyroelectric properties of bone

The voltage and time dependences of the pyroelectric properties of wet and dry bone (turkey femur) were investigated using Chynoweth´s (1956) dynamic pyroelectric method. The current generated by the sample had both real and imaginary components. The magnitude of the response was almost the same regardless of which sample electrode was irradiated with the laser beam, but the signs were opposite. The current increased by up to several orders of magnitude when a bias DC field of 1000 V/cm was imposed. When the bias field was switched off, a current in the opposite direction with a decay time of tens of hours was measured. There was also a slow decay of a direct current with a polarity opposite to that of the bias field. In conductivity measurements, the DC varied nonlinearly as the 1.5 power of the voltage. When the samples were stored in vacuum at 100°C for one hour, both the pyroelectric coefficient and the conductivity decreased by several orders of magnitude. It is concluded that the pyroelectric properties of bone depend strongly on the moisture content and that the polarization in wet bone is nonuniform. The polarization appears to be due to an internal field at the interfaces of the solid matrix and the fluid within the pores