Human beings are attracted to glossy objects. However, the investigation of whether this preference for glossy is a systematic bias, and the rationale for why, has received little or no attention. Drawing on an evolutionary psychology framework, we propose and test the hypothesis that the preference for glossy stems from an innate preference for fresh water as a valuable resource. In a set of six studies we demonstrate the preference for glossy among both adults and young children (studies 1A, 1B and 2) ruling out a socialization explanation, investigate the hypothesis that the preference for glossy stems from an innate need for water as a resource (studies 3 and 5) and, in addition, rule out the more superficial account of glossy = pretty (study 4). The interplay between the different perspectives, implications of the findings and future research directions are discussed.

Scheelite related compounds (A′,A″) n [(B′,B″)O4] m with B′, B″ = W and/or Mo are promising new light-emitting materials for photonic applications, including phosphor converted LEDs (light-emitting diodes). In this paper, the creation and ordering of A-cation vacancies and the effect of cation substitutions in the scheelite-type framework are investigated as a factor for controlling the scheelite-type structure and luminescent properties. CaGd2(1–x)Eu2x (MoO4)4(1–y)(WO4)4y (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) solid solutions with scheelite-type structure were synthesized by a solid state method, and their structures were investigated using a combination of transmission electron microscopy techniques and powder X-ray diffraction. Within this series all complex molybdenum oxides have (3 + 2)D incommensurately modulated structures with superspace group I41/a(α,β,0)00(−β,α,0)00, while the structures of all tungstates are (3 + 1)D incommensurately modulated with superspace group I2/b(αβ0)00. In both cases the modulation arises because of cation-vacancy ordering at the A site. The prominent structural motif is formed by columns of A-site vacancies running along the c-axis. These vacant columns occur in rows of two or three aligned along the [1̅10] direction of the scheelite subcell. The replacement of the smaller Gd3+ by the larger Eu3+ at the A-sublattice does not affect the nature of the incommensurate modulation, but an increasing replacement of Mo6+ by W6+ switches the modulation from (3 + 2)D to (3 + 1)D regime. Thus, these solid solutions can be considered as a model system where the incommensurate modulation can be monitored as a function of cation nature while the number of cation vacancies at the A sites remain constant upon the isovalent cation replacement. All compounds’ luminescent properties were measured, and the optical properties were related to the structural properties of the materials. CaGd2(1–x)Eu2x (MoO4)4(1–y)(WO4)4y phosphors emit intense red light dominated by the 5D0–7F2 transition at 612 nm, along with other transitions from the 5D1 and 5D0 excited states. The intensity of the 5D0–7F2 transition reaches a maximum at x = 0.5 for y = 0 and 1.

In this paper the luminescence of the scheelite-based CaGd₂(₁-x)Eu₂x(WO₄)₄ solid solutions is investigated as a function of the Eu content and temperature. All phosphors show intense red luminescence due to the ⁵D₀ - ⁷F₂ transition in Eu³⁺, along with other transitions from the ⁵D₁ and ⁵D₀ excited states. For high Eu³⁺ concentrations the intensity ratio of the emission originating from the ⁵D₁ and ⁵D₀ levels has a non-conventional temperature dependence, which could be explained by a phonon-assisted cross-relaxation process. It is demonstrated that this intensity ratio can be used as a measure of temperature with high spatial resolution, allowing the use of these scheelites as thermographic phosphor. The main disadvantage of many thermographic phosphors, a decreasing signal for increasing temperature, is absent.

No abstract

In this paper, with the example of two different polymorphs of KEu(MoO 4 ) 2 , the influence of the ordering of the A-cations on the luminescent properties in scheelite related compounds (A′,A″) n [(B′,B″)O 4 ] m is investigated. The polymorphs were synthesized using a solid state method. The study confirmed the existence of only two polymorphic forms at annealing temperature range 923−1203 K and ambient pressure: a low temperature anorthic α-phase and a monoclinic high temperature β-phase with an incommensurately modulated structure. The structures of both polymorphs were solved using transmission electron microscopy and refined from synchrotron powder X-ray diffraction data. The (23) o , q = 1/2a* + 1/2c*). In both cases the modulation arises due to Eu/K cation ordering at the A site: the formation of a 2-dimensional Eu 3+ network is characteristic for the α-phase, while a 3-dimensional Eu 3+-framework is observed for the β-phase structure. The luminescent properties of KEu(MoO 4 ) 2 samples prepared under different annealing conditions were measured, and the relation between their optical properties and their structures is discussed.