Starting from two wide band gap semiconductors AgTaO 3 and SrTiO 3 , we managed to reduce the band gap by forming their solid solutions, i.e. (AgTaO 3 ) 1-x (SrTiO 3 ) x (0.0 ≤ x ≤ 1.0). These solid solutions all adopt cubic perovskite structure similar to SrTiO 3 and high temperature phase of AgTaO 3 , suggesting that SrTiO 3 is helpful to stabilize AgTaO 3 in its high temperature cubic phase. Substantial improvements over photocatalytic hydrogen production were realized in these solid solutions which clearly outperform their parent compounds AgTaO 3 and SrTiO 3 . In-situ exolution of silver nanoparticles at the surface of solid solutions (x = 0.2) substantially strengthen the visible light absorption due to localized surface plasmons of these silver nanoparticles . This contributes to further improvements on both photocatalytic hydrogen and oxygen production under visible light illumination (λ ≥ 400 nm). Apparent quantum efficiency as high as ˜ 2.02% and ˜ 0.11% was achieved at solid solutions (x = 0.2) decorated with silver nanoparticles for full range (λ ≥ 250 nm) and visible light (λ ≥ 400 nm) illumination respectively. Photoelectrochemical analysis suggests that solid solutions own a better charge separation conditions than their parent compounds. Furthermore, the band edge positions of solid solutions (x = 0.2) lie approximately in the middle between AgTaO 3 and SrTiO 3 , being ideal for solar water splitting reactions.
Constituting solid solutions has been an appealing means to gain control over various physicochemical properties. In this work, we synthesized a series of SrTiO 3 -BiFeO 3 solid solutions and systematically explored their structural, optical and photocatalytic properties. Our results show that all solid solutions crystallize in a primitive cubic structure and their band gap values can be easily tuned by adjusting molar ratios between SrTiO 3 and BiFeO 3 . Photocatalytic hydrogen production under both full range and visible light irradiation is greatly improved after forming solid solutions. The highest hydrogen production rate obtained is ∼180 μmol/h under full range irradiation (λ ≥ 250 nm) and ∼4.2 μmol/h under visible light irradiation (λ ≥ 400 nm), corresponding to apparent quantum efficiency ∼2.28% and ∼0.10%, respectively. The activity is found to be strongly influenced by surface area and light absorption. Theoretical calculation suggests that Fe contributes to the formation of spin-polarized bands in the middle of original band gap and is responsible for the band gap reduction and visible light photocatalytic activity .
Currently, phosphor-converted LEDs (pc-LEDs) are revolutionizing the industry of plant growth lighting. To meet the requirements of this technology, phosphors with tunable photoluminescence , high thermal stability and luminous intensity are required. Herein, we found that the simple substitution of yttrium for lanthanum in La 2 MgTiO 6 :Mn 4+ (LMT:Mn 4+ ) system could satisfy above three criteria simultaneously. The photoluminescence properties can be regulated by continuously controlling the chemical composition of La 2-x Y x MgTiO 6 :Mn 4+ solid solution . The La sites are occupied by Y ions , causing a significant blue shift in the emission spectra which owing to the change of local crystal field strengthen. Meanwhile, the thermal stability and decay lifetimes are also varied due to the variation of local structure and band gap energy. The thermal stability of the material reaches 83.5% at 150 °C, which is better than the reported La 2 MgTiO 6 :Mn 4+ and Y 2 MgTiO 6 :Mn 4+ phosphors. The electronic luminescence (EL) of pc-LED devices using La 2-x Y x MgTiO 6 :Mn 4+ red phosphor is evaluated, which matching the absorption regions of plant pigments well, reflecting the superiority of the studied phosphors in plant growth lighting areas.
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