Turquoise monoclinic single crystals of the novel three‐dimensional Cu2[μ8‐O3P(CH2)2PO3]·3.2H2O coordination polymer were prepared using the silica gel method. Space group C2/m (no. 12) with a = 1483.6(2), b = 668.44(8), c = 436.30(6) pm, β = 93.28(2)°. The Cu2+ cation is coordinated by four oxygen atoms stemming from the 1,2‐ethylenediphosphonate dianions in a square planar manner and two water molecules in the axial positions. The connection between the Cu2+ cations and the [CPO3] units from the 1,2‐ethylenediphosphonate dianions leads to layers parallel to (100), which are linked by the ethylene groups to a three‐dimensional framework with channel‐like voids. The channel‐like voids accommodate water molecules not bound to Cu2+ and extend parallel to [001] with an opening of about 550 pm × 260 pm. Magnetic measurements reveal an antiferromagnetic behavior due to a superexchange coupling between Cu2+ ions through an oxygen bridge. The UV/Vis spectrum reveals three d–d transition bands at 694, 774, and 918 nm. The compound can be fully dehydrated by thermal treatment and rehydrated by storage in ambient air.
High‐k LTCC tapes with ultralow sintering temperatures were developed from lead‐free perovskite powders. Lowering of the sintering temperature from 1250°C down to 900°C has been achieved by means of ultrafine ceramic powders in combination with suitable sintering aids. The tape‐casting process has been optimized for ultrafine powders with an enhanced sintering activity. Low‐sintering high‐k tapes of a thickness down to 40 μm, suitable for LTCC processing, were obtained. The sintering behavior of these high‐k tapes has been studied and compared with other LTCC materials. Dielectric properties of the high‐k material have been investigated on a multilayer test structure consisting of up to 20 dielectric layers. After metallization with an Ag conductor, the green tapes were stacked and laminated. Sintering of these multilayer stacks at 900°C gives dense ceramic samples. Permittivities up to 2000 have been obtained, together with low dielectric losses. Material compatibility with several Ag/Au‐thick‐film‐paste systems has been tested.
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