A new polymorph of NaSbO(3) has been synthesized at 10.5 GPa and 1150 degrees C in a uniaxial split sphere anvil type press (USSA-2000) and recovered back to ambient conditions. The high-pressure form of NaSbO(3) adopts an orthorhombically distorted perovskite structure, isostructural with CaTiO(3), GdFeO(3), and NaTaO(3). The space group is Pnma, and the unit cell dimensions are a = 5.43835(6) A, b = 7.66195(8) A, c = 5.38201(5) A. It is a white insulator with an optical band gap of 3.4 eV. This compound represents the first ternary perovskite prepared containing Sb(5+) on the octahedral site. The octahedral tilting distortion in this compound is much larger than expected from ionic radii considerations. The distortion is driven by a second-order Jahn-Teller distortion originating on oxygen that can be traced back to strong Sb-O covalent bonding. A conflict arises between the strong covalent bonding interactions at oxygen that favor a large octahedral tilting distortion and the repulsive Na-O interactions that oppose excessive octahedral tilting. This conflict destabilizes the perovskite topology, thereby stabilizing the ilmenite polymorph under ambient conditions. Analysis of ionic and covalent bonding explains why ASbO(3) and ABiO(3) compositions frequently adopt structures that violate Pauling's rules.

A red phosphor, Li-doped Gd2O3:Eu3+ with high cathodoluminescent brightness was developed. In contrast to Gd2O3:Eu3+ which showed an irregular shape of agglomerated fine particles (the mean particle size <0.5 μm), the morphology of Li doped Gd2O3:Eu3+ crystals was quite regular and pseudospherical (the mean particle size ≈2 μm). In particular, the incorporation of Li+ ions into Gd2O3 lattice could induce a remarkable increase of cathodoluminescence efficiency at low voltages (500 V–1 kV). The highest emission intensity was observed with Gd1.84Li0.08Eu0.08O3−δ, whose brightness at 500 V was increased by a factor of 1.8 in comparison with that of commercial Y2O3:Eu3+. This phosphor may be an application to the field emission display operating at low voltages.

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The influence of Li doping on the crystallization behavior, morphology, and enhancement in photoemission intensity of Gd 2-x Y x O 3 :Eu 3+ solid-solution was investigated. To maximize an effect of the Li component which is volatile at elevated temperature, the citrate route was adopted for the synthesis at low temperature (650-850 °C). Firing the metal citrate precursor at 650 °C for 5 h was sufficient for the formation of 100 nm sized, nonaggregated, and spherical Li-doped Gd 2-x Y x O 3 :Eu 3+ particles, whose photoluminescence (PL) emission intensity is comparable with that of commercial red phosphor Y 2 O 3 :Eu 3+ . Such a temperature is much lower than the typical solid-state reaction or spray pyrolysis temperature (>1400 °C). Additional heat treatment up to 850 °C resulted in well-developed 500 nm sized pseudospherical particles whose PL brightness is close to ∼150% in comparison with that of commercial red phosphor. Li-doped Gd 2-x Y x O 3 :Eu 3+ appears to be a very promising red phosphor because the particle size and shape can be controlled at low temperature (650-850 °C) by the change of Y or Li contents without significant loss of brightness.