Tma 8310

The T_g was determined from thermomechanical analysis (TMA) at a heating rate of 10 °C min⁻¹ and under a 1.0 g loading using a TMA 8310 (Rigaku, Japan). The linear thermal expansion coefficient of the samples, measuring around 4 mm × 4 mm × 15 mm, was also evaluated using the same equipment at a temperature range of 200–350 °C. Moreover, the local coordination state of phosphorus was determined by measuring the ³¹P MAS NMR spectra using a CMX-400 NMR spectrometer (JEOL, Japan). A frequency, spin rate and pulse delay of 161.80 MHz, 10 kHz and 5 s, respectively, were used in the measurements. The chemical shifts were estimated with respect to H₃PO₄ in a D₂O solution (0 p.p.m.) and the conventional notation for phosphorus sites, Qⁿ, was used for the analysis. The n value denotes the number of bridging oxygens per PO₄ tetrahedron. Furthermore, the densities were measured by applying the Archimedes method using water at room temperature. We measured the refractive index of the samples using a prism coupler with a 473, 633, 1,319 and 1,553 nm light source (Metericon, NJ, USA); the error in the measurement was 10⁻⁴.

Linear thermal expansion ΔL(T)/L along with the horizontal direction was measured using a laser-interference dilatometer (LIX-2; Ulvac) with a warming process. ΔL(T)/L along with the vertical and the horizontal directions on both warming and cooling processes were measured using a thermomechanical analyzer (TMA8310; Rigaku). For sintered polycrystalline samples, ΔL/L is related directly to the volume (V) expansion in a manner of ΔL/L=(1/3)ΔV/V. Temperature-dependent resistivity ρ(T) was measured using a conventional four-probe method (PPMS: Quantum Design). Temperature-dependent magnetization M(T) was measured at 1T using a superconducting quantum interference device magnetometer (MPMS; Quantum Design).