Crystal structure, far-infrared spectroscopy, and microwave dielectric properties of two novel vanadates CaRECeV3O12 (RE = Nd, Sm)
Two novel low- ε r CaRECeV 3 O 12 (RE = Nd, Sm) microwave dielectric ceramics were prepared to utilize the solid-state method. According to XRD and Raman spectroscopy data, the CaRECeV 3 O 12 (RE = Nd, Sm) ceramics had a tetragonal zircon-type with an I 4 1 / amd space group. Dense CaNdCeV 3 O 12 and CaSmCeV 3 O 12 ceramics sintered at 1225 °C and 1200 °C showed ε r ∼11.85 ± 0.1 and 11.33 ± 0.1, Q × f ∼40,100 ± 500 GHz and 43,290 ± 500 GHz, τ f ∼ −27.2 ± 0.5 ppm/°C and −22.4 ± 0.5 ppm/°C, along with α L of 9.4 ppm/°C and 8.5 ppm/°C, respectively. The measured ε r and corrected ε r (corr) values were larger than ε r (C-M) (9.41 and 9.47) in CaNdCeV 3 O 12 and CaSmCeV 3 O 12 due to the cations being, on average, under-bonded and the overall structures being in a slightly expanded state. The slightly higher | < d > | value of CaNdCeV 3 O 12 led to its higher ε r (corr) value, even though it had a lower α D /V m value. The sign and magnitude of τ f values for CaNdCeV 3 O 12 and CaSmCeV 3 O 12 were mainly determined by their positive temperature coefficients of dielectric polarizability τ αm of +36.2 ppm/°C and +32.1 ppm/°C, respectively. The inherent dielectric constant and dielectric loss were examined using far-infrared reflectivity spectra, Raman spectra, and the packing fraction.
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