Modified structure and optical band-gap in perovskite ferroelectric (1-x)KNbO3-xBaCo1/3Nb2/3O3 ceramics

Crystal Structure, Phase Transitions and Photoferroelectric Properties of KNbO3-Based Lead-Free Ferroelectric Ceramics: A Brief Review

“…More recently solid solutions of KN with BaNi 1/2 Nb 1/2 O 3−x (Grinberg et al, 2013;Zhou et al, 2014;Hawley et al, 2017), BaCo 1/2 Nb 1/2 O 3−x (Yu et al, 2016, BaCo 1/3 Nb 2/3 O 3 (Si et al, 2018), BaNb 1/2 Fe 1/2 O 3−x have been investigated as potential materials for photo-induced applications, including photovoltaic applications. The photoferroelectrics characteristics of KN-based ceramics is therefore reviewed in the next section.…”

“…Grinberg et al (2013) measured a modest short-circuit photocurrent, J sc , of 0.1 µA.cm −2 and open-circuit photovoltage, Subsequently, Elicker et al (2018) also found a similar degree of bandgap narrowing (i.e., a 0.9-1 eV) in the K 1−x La x Nb 1−x Fe x O 3 (KNLF) system, suggesting that the electronic lone-pair in Bi 3+ may play a negligible role in the physics of bandgap narrowing of KN, as shown on Table 5. These researchers fabricated FEPV devices from KNBF and KNLF (x = 0.32), which combined with a redox couple (I − /I 3− ) exhibited a typical diode-like behavior, showing J sc and V oc values of 0.115 µA and 0.075 V for KNBF and 0.19 µA (Grinberg et al, 2013) 3.1 (direct) (Zhou et al, 2014) BaCo 1/2 Nb 1/2 O 3−x (x = 0.4) 2.4 (direct) (Yu et al, 2016) BaCo 1/3 Nb 2/3 O 3 (x = 0.25) 2.44 (direct) (Si et al, 2018) BaNb 1/2 Fe 1/2 O 3−x (x = 0.1) 2.48 (direct) and 0.035 V for KNLF, respectively. More recently, Han et al studied the (1-x) KNbO 3 -xBaFeO 3−δ (x = 0.00-0.10) system and reported a minimum optical bandgap of approximately 1.82 eV for x = 0.10.…”

First principles study for band engineering of KNbO3 with 3d transition metal substitution

“…Recently researchers have made further efforts in exploring inorganic perovskite CsPbI 3 for photovoltaic application, through tentative substitutions of Pb to avoid toxicity and iodine to address instability issues. [5][6][7] Previous work [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] suggested that inorganic and nontoxic multiferroic perovskite semiconductors, particularly oxide based systems, could be better alternatives for solar cell applications, owing to their high stability with adjustable bandgap and carrier concentrations through doping or alloying. Generally, a typical wide gap perovskite is based on the conguration of ABO 3 , with A being an alkaline-earth metal or alkali metal element and B a transition metal.…”

“…They concluded that the Ni octahedral energy splitting in BTCN resulted in bandgap reduction. 21 On the basis of the substitutional model by Grinberg et al, various co-doping efforts were then made experimentally, covering Ba + Fe, 22 Ba + Co, 23,24 Ba + Ni [25][26][27] and Ba + Zn 28 in KNbO 3 , though the impacts of the subsequent work was limited due to the lack of systematic understanding for electronic structures.…”

Crystal structures and electrical properties of Sr/Fe‐modified KNbO3 ferroelectric semiconductors with narrow bandgap

“…Compared with the perovskite halide ferroelectrics, perovskite‐oxide ferroelectrics have exhibited broader applications in the photovoltaic field owing to their advantages of superior stability 11 . However, most conventional oxide ferroelectrics have higher bandgaps ( E g > 3.0 eV), which leads to light absorption primarily in the ultraviolet region 12,13 . Therefore, the reduction in bandgap in ferroelectrics is important.…”