TY - JOUR
T1 - Crystal and defect chemistry influences on band gap trends in alkaline earth perovskites
AU - Lee, Soonil
AU - Woodford, William H.
AU - Randall, Clive A.
N1 - Funding Information:
This study is based on work supported by the National Science Foundation, as part of the Center for Dielectric Studies under Grant No. 0628817. Dr. Mike Chu of Ferro Corporation is acknowledged for making ratio measurements with XRF on the nonstoichiometry study.
PY - 2008
Y1 - 2008
N2 - A number of perovskites with A -site alkaline earth chemistries being Ca, Sr, and Ba, and tetravalent cations including Ce, Zr, and Ti are measured for optical band gap and found to vary systematically with tolerance factor and lattice volume within limits defined by the chemistry of the octahedral site. This paper also focuses on the BaTi O3 system, considering equilibrated nonstoichiometries, and determines the changes in band gap with respect to BaTi ratios. It was found that the optical band gap changes in the solid solution regime and is invariant in the second phase regions, as would be expected. In the cases of BaTi<1.0, the variation in band gap scales with lattice volume, but in the BaTi>1.0 stoichiometries, there is a distinct Urbach tail and the trend with lattice volume no longer holds. It is inferred that the VTi -2 VO partial Schottky complex controls the band gap trend with Ba-rich nonstoichiometries.
AB - A number of perovskites with A -site alkaline earth chemistries being Ca, Sr, and Ba, and tetravalent cations including Ce, Zr, and Ti are measured for optical band gap and found to vary systematically with tolerance factor and lattice volume within limits defined by the chemistry of the octahedral site. This paper also focuses on the BaTi O3 system, considering equilibrated nonstoichiometries, and determines the changes in band gap with respect to BaTi ratios. It was found that the optical band gap changes in the solid solution regime and is invariant in the second phase regions, as would be expected. In the cases of BaTi<1.0, the variation in band gap scales with lattice volume, but in the BaTi>1.0 stoichiometries, there is a distinct Urbach tail and the trend with lattice volume no longer holds. It is inferred that the VTi -2 VO partial Schottky complex controls the band gap trend with Ba-rich nonstoichiometries.
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U2 - 10.1063/1.2936091
DO - 10.1063/1.2936091
M3 - Article
AN - SCOPUS:44349096871
SN - 0003-6951
VL - 92
JO - Applied Physics Letters
JF - Applied Physics Letters
IS - 20
M1 - 201909
ER -