The off-axis pyroelectric effect observed for lithium tetraborate

We find a pyroelectric current along the 〈110〉 direction of stoichiometric Li2B4O7 so that the pyroelectric coefficient is nonzero but roughly 10−3 smaller than along the 〈001〉 direction of spontaneous polarization. Abrupt decreases in the pyroelectric coefficient along the 〈110〉 direction can be correlated with anomalies in the elastic stiffness C33D contributing to concept that the pyroelectric coefficient is not simply a vector but has qualities of a tensor, as expected. The time dependent surface photovoltaic charging suggests that an inverse piezoelectric effect occurs at the (110) surface but not the (100) surface. Both effects along the 〈110〉 direction or at the (110) surface are distinct the conventional as a bulk pyroelectric effect.