Cao Renping,Jiao Yuming,Wang Xuantian,Ouyang Xun,Chen Ting,Wan Huijun,Fan Ting,Xie Shikun
In this work, CaTiSiO 5 :Ce 3+ and CaTiSiO 5 :Ce 3+ , Mn 2+ phosphors are prepared in air via the high-temperature solid-state reaction method. The crystal structure, phase purity, and luminescence properties of the samples are investigated. CaTiSiO 5 :Ce 3+ phosphor under excitation at 320 nm emits mazarine light with chromaticity coordinates (0.1693, 0.0053) and optimal Ce 3+ doping concentration of ∼ 6 mol.%. CaTiSiO 5 :6%Ce 3+ , Mn 2+ phosphor with excitation at 320 nm shows a tunable color emission from yellow to red-orange with increasing Mn 2+ concentration from 1 mol.% to 8 mol.%, the corresponding chromaticity coordinates are changed from (0.4302, 0.4507) to (0.5475, 0.3916), and the corresponding lifetimes decrease from 34.22 ns to 16.33 ns. The energy transfer (ET) process between Ce 3+ and Mn 2+ ions is confirmed by the spectral properties and lifetimes of CaTiSiO 5 :6%Ce 3+ , Mn 2+ phosphor, with ET efficiency reaching ∼ 52.28%. The luminescence mechanism is explained by the energy level diagrams of Ce 3+ and Mn 2+ ions. The experimental results are of benefit for research and improving the tunable emission of other phosphors.
The CaTiSiO 5 -based ceramics show promise as dielectric materials for high-temperature MLCC due to their excellent temperature stability which is expected to be improved by co-doping at the A/B sites. In this study, the Dy and Al co-doped CaTiSiO 5 ceramics (Ca 1− x Dy x Ti 1− x Al x SiO 5 , x = 0, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08) were fabricated by the conventional solid-state method. The effects of Dy and Al co-doping on the phase structures, dielectric properties and impedance characteristics, were investigated in detail. CaTiSiO 5 -based ceramics transformed to the paraelectric phase and achieved excellent temperature stability of permittivity by Dy and Al doping, which results from the long-range disorder in the arrangement of Ti displacements within the octahedral chain. Components with x = 0.01 showed linear dielectric response under the electric field. It obtained a high and stable dielectric constant in a wide temperature range ( ε r = 52, TCC ≤ ± 180 ppm/°C over the temperature range from − 55 to 300 °C), low loss (tan δ < 0.07), high breakdown strength (∼ 516 kV/cm) and high DC resistance ( ρ = 3.8 × 10 10 Ω cm at 300 °C).
The unique antipolar structure of titanite-type CaTiSiO 5 -based ceramics has attracted considerable attention, with certain compositions confirmed to be antiferroelectric. Due to their low relative permittivity, CaTiSiO 5 ceramics hold promise for electrically tunable applications, but their reliability and high dielectric loss under DC bias must be improved. Herein, the introduction of Mn in CaTiSiO 5 slightly perturbs the long-range ordered antipolar TiO 6 chains, creating antipolar microdomains at a scale of tens of nanometers. This structural adjustment markedly lowers the dielectric loss under DC bias without substantially sacrificing the tuning performance. Moreover, Mn doping promotes a carrier migration barrier at the electrode–ceramic interface, which raises the breakdown strength. With 2 mol% MnO 2 addition, the ceramic sample achieves a tunability above 50% under 250 kV/cm and maintains tan δ < 0.002 at 100 kHz. Compared with CaTiSiO 5 -SiO 2 composite ceramics, the domain-engineering strategy outperforms conventional composite approaches for reducing dielectric loss. Thus, tailoring antipolar domains offers an effective route to enhance the overall properties of antiferroelectric tunable ceramics, providing a new perspective for developing next-generation tunable materials and devices.
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