We find a pyroelectric current along the 110 direction of stoichiometric Li 2 B 4 O 7 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 C D 33 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.

The band structure of Li2B4O7(100) and Li2B4O7(110) was experimentally determined using a combination of angle-resolved photoemission and angle-resolved inverse photoemission spectroscopies. The experimental band gap depends on crystallographic direction but exceeds 8.8 eV, while the bulk band gap is believed to be in the vicinity of 9.8 eV, in qualitative agreement with expectations. The occupied bulk band structure indicates relatively large values for the hole mass; with the hole mass as significantly larger than that of the electron mass derived from the unoccupied band structure. The Li2B4O7(110) surface is characterized by a very light mass image potential state and a surface state that falls within the band gap of the projected bulk band structure.

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Petrosky, J. C.; McClory, J.; Burak, Ya. V.; Adamiv, V. T.; and Dowben, Peter A., "The surface core level shift for lithium at the surface of lithium borate" (2009 Keywords:Oxide dielectric layers Lithium tetraborate Surface-to-bulk core level shift a b s t r a c t The shallow Li 1s core level exhibits a surface-to-bulk core level shift for the stoichiometric Li 2 B 4 O 7 (11 0) surface. Angle-resolved photoemission spectroscopy was used to indentify Li 1s bulk and surface core level components at binding energies À 56.5 7 0.4 and À 53.7 7 0.5 eV, respectively. We find photoemission evidence for surface states of Li 2 B 4 O 7 (11 0) that exist in the gap of the projected bulk density of states. The existence of surface states is consistent with the large surface-to-bulk core level shift for the Li 1s core.

High-temperature coherent neutron powder diffraction experiments were carried out on Li2B4O7 with boron isotope ratio 11B : 10B as high as 99.6 : 0.4%. Neither traces of phase transformations nor discontinuous changes of physical properties were observed. Anomalies in the thermal expansion of lithium tetraborate were considered in terms of first-order Grüneisen approximation. Extended bond length analysis revealed significant modifications of the boron–oxygen framework which is supplemented by dynamic lithium disorder. Impedance spectroscopy studies revealed a complicated conduction mechanism in single crystalline lithium tetraborate. The lithium diffusion pathway for bulk conductivity along the polar axis was established using both maximum entropy and anharmonic refinement techniques.